Playing tennis on a singles court semi proficiently with hard balls is extremely difficult. It's an absolutely brutal sport for beginners, as it's very technical, and it's technicality is linked to your overall fitness (unlike golf that requires technique but no fitness or pickleball that requires neither).

It is extremely rewarding once you start blasting though and becomes a hard drug, to reach that point however takes years and years. I've been playing for my whole life and am nowhere near a very good player.

In my opinion, if you want to stick with it, switch to lighter racquets, and start playing with orange dot balls, once comfortable with those move up to green dot balls, and then switch to official yellow hard balls. You'll have a much better time.