The faster you get, the harder it is to improve. I'm stuck at 22:30 for over a year, so I feel you. I would recommend following a proper training plan, at this stage, or making up one of your owns. Just trying to run 5k in training as fast as you can will not do it. I would recommend a 4-5 days training split; I am not very experienced in training for a 5k, so I can not tell you interval durations (however, 400m splits and 800m splits intervals should do it) and I would say tone down on the long run (you don't really need to run >20k/run when your goal is a 5k), but, you should think it like this:
Choose a goal race/goal day. You train and when you reach peak training is when you need to expect to break your PB.
Follow the plan and, remember, keep your easy days easy so you can make your hard days hard.
A 4-5 day split would be: (a) one day easy run, 30-40 minutes; (b) one day workout (intervals, fartlek); (c) one day tempo run (20-30 minutes tempo) - don't forget about warm up and cool down on these days; (d) long run:10-15k should do it for you; (e) if you have a fifth day, keep it easy.
The plan I mentioned is something you should also work up to. Don't go from running 20k per week to running >40 with two hard workouts. You work up. You get the number of runs. You increase the volume. You add one workout. Etc. Proper training plans are supposed to be done after a period of base building, that is, a period of volume accumulation, so you don't risk injury.
The ideas I gave are quite general and if you want better/more precise, as I said, there are quite a lot of books and plans out there. I am not fast, objectively speaking and I lack proper 5k race training (I ran my 5k PB during a 10K race), so take this with a grain of salt.
Best of luck.