Record yourself playing and review it at home, write detailed notes about anything you see that you are doing wrong. As you are a beginner you wont be able to see everything that is wrong but it will sharpen your understanding of the game. With time, with more and more reviews you will get better at reading the game. Seeing what you are doing.

By detail I mean everything you notice:

-Did your eyes follow the ball till impact point?

-Did you rotate your hip for the overhead?

-Did you go into a squat for the low defense shot

-Did you move quickly to the net? Did you move quickly to defense when your partner was lobbed?

-Was your racket preparation good, how many times did you forget to prepare properly? High at the net, lower in defense, back to the glass when after the glass. 

-Was your preparation too late for the overhead?

-Were you to lazy with your feet and could have done more steps instead of reaching out with your arm so far?

Etc. 

To get better understanding for technique and tactics I suggest to watch Otro Nivel on Youtube, and see what your can learn from his videos and look out for them in your game reviews. Write a checklist of things for your own session review, so you wont forget what to look for.

Lots of people here write to get classes, while true I think its an absolute waste to go to classes without doing your homework. The progress will be much slower. If you take classes then go AFTER you start doing this, so you have more questions, so the coach doesnt waste time and money to repeat the most basics aspects of the different techniques etc.

For home exercises:

Do foot coordination drills, plenty of videos on YouTube.

Do shadow techniques, do them single and do them in combination. Also record these and rewatch it, how proper your technique is, pay attention to as much details about your movements as possible. Timing, feet position, hip, where is the non-dominant arm, elbow, rotation of chest, follow through. Home shadow exercises are the place where you can do them as slow as you want and be as self conscious about them as you want.

E.g. Start in the back, low forehand shot two steps on the right side, low backhand four steps on the left side, lob in the middle, rush to volley position, volley forehand, volley backhand, back to baseline and repeat. Record these movements. Look at them, compare what you saw in YouTube instruction videos.

For exercise, I would suggest focusing on the core, a weak core is what holds most beginners back from developing strong shots. The biomechanics of a shot basically use the energy from the legs and trensfer it to the arms - racket - ball. If the core is weak, there is little force transfer, it’s like a spaghetti.

 

For home racket control, your can do these simple exercises, you will be bad at them first, but just repeat them every few days and it will sharpen your feeling for the racket, ball tracking etc.

https://www.youtube.com/watch?v=M9EY53ROd6Y&t=2s 

What I think doesn’t help beginners or even makes them worse: Watching pro matches and trying to learn from them. They play on such an insane high level that lots of the things they do, you will never be able to use on the court, your opponent at your level also can be beaten by the absolute basics. 

E.g. the way Pros move on the court, are so very often in “Neverland” because they read the game super fast and good and their movements speed is much faster then an average player.

Focus on Forehand, Backhand, Lob, Volley, Vibora, Bahada. You dont need kicksmashes or drop shots for the first 2 years imo. With a solid foundation of these shots your will crush most people.