OpenCart Community

Hi, since I have to much problems with the update I guess it's better to do a clean v3 install and move all the data.
I already have a working v3 (coming from v2) but I get to many probs with all kinda things (I might be asking support here for months I guess )
So I want to do it the clean way ;-)

How can I do this easy ?
- the import/export db tool gives an error at import, so that's no option
- Should I do it in the database and copy the products or customers tables?

I've gotten so far to import export all products and their variables via the excel importer.
Only there's a problem with the customers, I cannot import them.
Even queries SQL give errors (I was able to run the other tables but OC_customer gives import errors.
How can I transfer the customers?