Sorry, should have read: without messing things up..

I would like to rename the sub folder that my shop is installed and running (over a year now) for Seo purposes.

Instead of reading mysite.com/shop I'd like it to read mysite.com/mykeyword

Are there any problem in doing this? Would there be any other files that the name would have to be changed?

One of the practical problems, is that all of the pages that are currently indexed by search engines, would then bring up a 'page not found' error message when people click on those search engine links. That would be resolved once all the search engines re-index your site pages, but realistically that could take anything up to a few weeks for them to all complete that task.

Hello Martine,

You can use what is called a '301 redirect' for that. It directs visitors and search engines from the old to the new URL. You can do that manually or, assuming you are on an Apache server, use Website Access Manager to do that for you.