Improving Tennis Reflexes and Stamina

I'm just really confused where to start. I research exercises for tennis stamina and I understand that sprints and HIIT are very important, but would soccer stamina help for tennis? I'm just wondering because there's way more soccer stamina advice and drills than tennis specific, so it'd be convenient if I could utilize those exercises.

Also, I'd really appreciate any advice on improving reaction time for a somewhat experienced player. I'm currently sitting at around a 7.2 UTR, and I'm trying to get my reaction time better so I can compete with higher level players because that's the main reason I'm struggling with them. It just feels like the ball is too fast. I tried researching online and I see some reaction balls and stuff, but is there anything specific I can do to really improve reaction time fast.

Any tips and advice would be much appreciated. Thanks!