You're not doing anything wrong. Your opponents are being rude.
In 15|10 games (15 minutes plus 10-second increment), taking 30 seconds to a minute per move is perfectly reasonable. You have time in the bank. You're not stalling. You're thinking.
The pressure you're feeling is just online chess culture at its worst. Some players get impatient with newer opponents and act like every blitz game is a bullet sprint. They don't care that you're learning. They want their win fast.
Here's the truth: take the time you need. You're a beginner trying to improve. That requires thought. If your opponents wanted faster games, they should play bullet or faster time controls. They chose 15|10. They have to accept that people will use those 15 minutes.
Don't let them rush you into bad moves or faster thinking than you're ready for. Chess rewards patience. Your opponents rushing you are the ones doing something wrong, not you.
Keep thinking. Keep learning. Ignore the complaints. If the toxicity bothers you too much, mute chat or switch to a different site. But don't speed up your games just because strangers online are impatient.