Please can i get advice-running faster

Im currently half marathon training. Got 4 weeks to go abd my long run is already at 19k.distance is fine for me...but im slow

So im trying to do some speed training. Im basically running 2 lamp posts fast. Then jog to recover. You can see my workout below

Am i doing this right is basically my question. Thankyou

https://connect.garmin.com/modern/activity/1170064692?share_unique_id=1