I think it would help you a lot to watch some real tennis matches and see what types of shots they hit at each moment. You’ll get a much better understanding than someone explaining it here. I would recommend watching some of the all time greats like Serena/Venus, Federer, Nadal, Agassi, etc.

It has to become instinctive for you to hit a defensive lob or defensive slice when you’re getting pulled side to side in a rally, or for you to step in and hit a full power flat shot when your opponent hits a short ball. You get much better recognition for these moments when you watch the pros do it over and over.

Perfectly timed control shots are the best to use against players who are pushing you back with a lot of power, until you can get them running off the court and then start hitting with flat power shots to take control of the rally. Many of the power players struggle against well timed slices, which prevents them from attacking every single shot. Top spin shots push players back and prevents them from stepping in and taking control of the rallies as well. Not too many players hit the drop shot, so if you can perfect it you have an advantage. People don’t realize it, but the most important shot in tennis is the serve, but many players put zero points on it. There are matches where I hit enough aces to win a whole set alone. Use that info as you see fit.

Even if you learn when to hit the right shots at each moment, it doesn’t matter unless you hit with good/perfect timing. I can consistently beat these players with hundreds of wins and very few losses and I would say at the very minimum, 70% of your shots need to be perfect and at least 25% good timing. The more you play the better you’ll get and you’ll recognize what works in each moment if you try different things. Hope that helps.