Hi OP, the first ground stroke after a serve can be difficult because you're recovering from your serve and the ball could be coming back at a pretty good clip, especially if you've really put a good first serve in.
A couple of thoughts:
- Try to make sure that you recover as quickly as possible after your first serve. The more balanced you can be at the end of the serve the faster you'll be able to recover.
- You might want to think about a conservative shot for the first ball after the serve just to get the rally going. Your opponent survived your serve - good on them - and you're still recovering.