I am new using the OS and I have a problem with my keyboard

I installed Zorin OS on an old Toshiba Satellite laptop, It works well, but sometimes the key for the letter 'r' 'y' and the number 5 don't work.

I don't really know what to do and I would really appreciate your help in fixing this.

Hello and welcome to the forum:)

Are those key work in another OS?
You can test it by Live USB session of other distro.

Yeah. Actually just before I switched to Zorin I was working with my laptop and no problem. That's what I don't get. because sometimes after a while it works again

Can you try update system, maybe you can try some lts kernel

Do you have alternative Numeric keypad overlaid on those keys?
Check NumLk or similar is not set.
Another user some time ago had a similar problem due to multiple purpose keys set to numeric mode.