Good evening Sofia and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the issues you have dealt with while trying to install our plugins.
I would love to help you with this topic.
Basically, the original message is saying that matching versions of the Events Calendar plugins is required for things to work properly.
The simplest solution is to deactivate all of our plugins and then delete them.
If you want to be on the safer side of things, you might want to do a database backup first, but it should not be necessary.
Once that is down, you can simply install them from scratch with the latest version and everything should be smooth sailing.
Let me know how that goes.
Best regards,
Geoff B.