Error must enter table prefix, valid user

Good afternoon,

Yesterday I was trying to install a new WordPress web page. I have MAMP PRO activated and I use PHP Storm. When I get into setup page I have to put the data base, etc. I fill all the things and I have checked that I have created the Data Base. When I press submit then I get the error: you must enter a table prefix. I have tried many times, with wp_, as_… but I still get the error. My MySQL version is 5.6.35 and PHP is 7.1.1.

When I try to fill wp-config and I get into setup page, then I have to insert again some information. When I submit the form, I had the error: insert a valid email address. Today I still have the same error but, now is not the email, is the username.

¿What can I do?
I’m so lost…

Thanks for all