diff --git a/internal/broker/core.go b/internal/broker/core.go
index f9b0a8b..fb2545c 100644
--- a/internal/broker/core.go
+++ b/internal/broker/core.go
@@ -2,45 +2,220 @@ package broker
 
 import (
 	"context"
-	"time"
-
 	"github.com/arcana261/ubroker/pkg/ubroker"
 	"github.com/pkg/errors"
+	"sync"
+	"time"
 )
 
-// New creates a new instance of ubroker.Broker
-// with given `ttl`. `ttl` determines time in which
-// we requeue an unacknowledged/unrequeued message
-// automatically.
 func New(ttl time.Duration) ubroker.Broker {
-	return &core{}
+	//return &core{}
+	core := &Core{
+		deliveryEntry:    make(chan ubroker.Delivery, 100),
+		requeueEntry:     make(chan requeue),
+		publishEntry:     make([]request, 100),
+		acknowledgeEntry: make([]int, 100),
+		ttl:              ttl,
+		delivered:        false,
+		isClosed:         false,
+		close:            false,
+		id:               0,
+	}
+	return core
 }
 
-type core struct {
+type Core struct {
 	// TODO: add required fields
+	ttl              time.Duration
+	deliveryEntry    chan ubroker.Delivery
+	requeueEntry     chan requeue
+	publishEntry     []request
+	acknowledgeEntry []int
+	delivered        bool
+	isClosed         bool
+	close            bool
+	id               int
+	queueGroup       sync.WaitGroup
+	syncCore         sync.Mutex
+}
+type request struct {
+	msg     ubroker.Delivery
+	ttlTime time.Time
+	error   chan error
+}
+type acknowledge struct {
+	id    int
+	error chan error
+}
+type requeue struct {
+	id    int
+	error chan error
 }
 
-func (c *core) Delivery(ctx context.Context) (<-chan ubroker.Delivery, error) {
+func (core *Core) startRequest() error {
+	core.syncCore.Lock()
+	if core.IsClosed() {
+		return ubroker.ErrClosed
+	}
+	defer core.syncCore.Unlock()
+	core.queueGroup.Add(1)
+	return nil
+}
+func (core *Core) IsClosed() bool {
+	if core.close == true {
+		return true
+	} else {
+		return false
+	}
+}
+func (core *Core) Delivery(ctx context.Context) (<-chan ubroker.Delivery, error) {
 	// TODO:‌ implement me
-	return nil, errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	//return errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if ctx.Err() == context.Canceled {
+		return nil, ctx.Err()
+	}
+	if ctx.Err() == context.DeadlineExceeded {
+		return nil, ctx.Err()
+	}
+	core.queueGroup.Add(1)
+	defer core.queueGroup.Done()
+	core.syncCore.Lock()
+	defer core.syncCore.Unlock()
+	if core.isClosed == true {
+		return nil, ubroker.ErrClosed
+	}
+	core.delivered = true
+	return core.deliveryEntry, nil
 }
-
-func (c *core) Acknowledge(ctx context.Context, id int) error {
+func (core *Core) Acknowledge(ctx context.Context, id int) error {
 	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Acknowledge is not implemented")
+	//return errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if ctx.Err() == context.Canceled {
+		return ctx.Err()
+	}
+	if ctx.Err() == context.DeadlineExceeded {
+		return ctx.Err()
+	}
+	core.syncCore.Lock()
+	defer core.syncCore.Unlock()
+	if core.isClosed == true {
+		return ubroker.ErrClosed
+	}
+	if core.delivered == false {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	}
+	var index = -1
+	for counter, message := range core.publishEntry {
+		if message.msg.ID == id {
+			index = counter
+			break
+		}
+	}
+	var ackId = -1
+	for counter, ids := range core.acknowledgeEntry {
+		if ids == id {
+			ackId = counter
+			break
+		}
+	}
+	if index == -1 {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	}
+	if ackId != -1 {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	}
+	if time.Now().Sub(core.publishEntry[index].ttlTime) > core.ttl {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	} else {
+		core.acknowledgeEntry = append(core.acknowledgeEntry, id)
+		return nil
+	}
 }
-
-func (c *core) ReQueue(ctx context.Context, id int) error {
+func (core *Core) ReQueue(ctx context.Context, id int) error {
 	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method ReQueue is not implemented")
+	//return errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if ctx.Err() == context.Canceled {
+		return ctx.Err()
+	}
+	if ctx.Err() == context.DeadlineExceeded {
+		return ctx.Err()
+	}
+	core.syncCore.Lock()
+	defer core.syncCore.Unlock()
+	if core.isClosed == true {
+		return ubroker.ErrClosed
+	}
+	if core.delivered == false {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	}
+	var index = -1
+	for counter, message := range core.publishEntry {
+		if message.msg.ID == id {
+			index = counter
+			break
+		}
+	}
+	if index == -1 {
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	}
+	if time.Now().Sub(core.publishEntry[index].ttlTime) > core.ttl {
+		_ = core.reRequest(core.publishEntry[index])
+		core.publishEntry = append(core.publishEntry[:index], core.publishEntry[index+1:]...)
+		return errors.Wrap(ubroker.ErrInvalidID, "Error")
+	} else {
+		_ = core.reRequest(core.publishEntry[index])
+		core.publishEntry = append(core.publishEntry[:index], core.publishEntry[index+1:]...)
+		return nil
+	}
 }
-
-func (c *core) Publish(ctx context.Context, message ubroker.Message) error {
+func (core *Core) reRequest(req request) error {
+	core.id = core.id + 1
+	var newMessageBroker ubroker.Delivery
+	newMessageBroker.Message = req.msg.Message
+	newMessageBroker.ID = core.id
+	var newMessage = request{}
+	newMessage.msg = newMessageBroker
+	newMessage.ttlTime = time.Now()
+	core.publishEntry = append(core.publishEntry, newMessage)
+	core.deliveryEntry <- newMessageBroker
+	return nil
+}
+func (core *Core) Publish(ctx context.Context, message ubroker.Message) error {
 	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Publish is not implemented")
+	//return errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if ctx.Err() == context.Canceled {
+		return ctx.Err()
+	}
+	if ctx.Err() == context.DeadlineExceeded {
+		return ctx.Err()
+	}
+	core.syncCore.Lock()
+	defer core.syncCore.Unlock()
+	if core.isClosed == true {
+		return ubroker.ErrClosed
+	}
+	//request{message,0,""}
+	//_ = core.reRequest(core.publishEntry[request{message,0,""}])
+	core.id = core.id + 1
+	var newMessageBroker ubroker.Delivery
+	newMessageBroker.Message = message
+	newMessageBroker.ID = core.id
+	core.deliveryEntry <- newMessageBroker
+	var newMessage = request{}
+	newMessage.msg = newMessageBroker
+	newMessage.ttlTime = time.Now()
+	core.publishEntry = append(core.publishEntry, newMessage)
+	return nil
 }
-
-func (c *core) Close() error {
+func (core *Core) Close() error {
 	// TODO:‌ implement me
-	return errors.Wrap(ubroker.ErrUnimplemented, "method Close is not implemented")
+	//return errors.Wrap(ubroker.ErrUnimplemented, "method Delivery is not implemented")
+	if core.isClosed {
+		return nil
+	}
+	core.syncCore.Lock()
+	defer core.syncCore.Unlock()
+	core.isClosed = true
+	close(core.deliveryEntry)
+	return nil
 }