The sport of football is one that requires a lot of training in order to be good at it.
Not only do you need to be strong but you need to be able to generate a lot of power all while having good agility to manoeuvre around opponents.
To develop the strength and power side during your football training concentrate on lifting heavy weights during your strength training exercises but moving as quickly as you can through the concentric portion of it (the first part of the exercise). This will help you to be able to generate a maximum amount of force over a short period of time, otherwise known as power.
The sport of football also requires excellent agility abilities because you constantly have to run around opponents who are trying to tackle you. To improve this skill you could do an exercise where you set out staggered pylons on a field. Next try and run through the field, around your pylons, while having other people act as opponents who try and stop you. This will give you great sport-specific practice that you can then transfer over to the game.
You will also want to work on developing strong muscles surrounding your kneecaps as well since with all this manoeuvring you will be doing there is a good chance your knee may not be tracking properly. This will cause a lot of pain and potential injury if your muscles are not strong enough so it is vital you include squats and lunges in your workouts.
As long as you are dedicated towards your training for this sport there is no reason you should not see an improvement from year to year. Just keep yourself motivated and be sure to get in proper nutrition for recovery and you will be well on your way.