What are the limits of space for the forms?

I had created a test form but It brings a message that it is out of space, but I don´t know exactly why am I out of space (i.e. many fileds, files too big). I need to know why and if it can be resolved by buying a paid plan, and which plan woud that be. 

Your account is currently in over limit status. Your upload space is 111.88MB. Under the Free plan, you only have 100MB storage space. The storage space is where the uploaded files from your users are located.

You can upgrade to Bronze plan to increase your storage space to 10GB. Here's a guide on How-to-Upgrade-My-Account.

You may also delete the submissions that has uploaded files in order to clear your storage space. Here's a guide: How-to-Delete-Form-Submission-Data.

Also, please purge the deleted forms in your Trash folder.

Hope that helps. Thank you.