It is normal that you need to make tactical changes during a game. You will see that while the game is taking place, at the bottom of the field between the two technical areas there is a blue button. If you click on it you will be allowed to make up to 3 substitutions per game and also change aspects of your line-up.
Next to your technical area there is a miniature field with some arrows that indicate your mindset and intensity. If you click on them, you can also edit these two aspects of your team.
For further information, click here.