Thank you, Javier, for your question!
It’s quite common that students have problems with ‘plenty’. Remember that:
Enough = sufficient
A lot = a high degree or number
Plenty = more than sufficient
We normally say ‘plenty…for something’ or ‘plenty… to do something’.
There are plenty of chairs for the meeting.
We have plenty of time to have a cup of coffee.
A common mistake occurs when a student says ‘there were plenty of people at the beach’.
A native speakers who hears this phrase will think, ‘plenty of people for what?’.
I hope that this is enough explanation for you. There have been plenty of people that have had the same problem as you, so don’t worry. Keep studying and practicing!