Missing posts and media after new installation

Hey,
I had trouble with my wordpress site that I was only able to fix with a complete new installation (I tried all the options from the normal troubleshooting and even the manual update instructions). Before I made a backup of my complete wordpress installation. I did the installion of wordpress into the database “usr_web46_1”. Then I imported my old database from my backup. The name of that database is “usr_web46_3”. When I imported the old database everthing went fine and I had no error messages. But still I don’t see any of my old posts under /wp-admin. I think there is some configuration missing but don’t know what and how to do it. I have not used my old wp-config.php file until now.

Also I cannot see any pictures I uploaded under media, but my child theme can be found under themes as well as the plugins I used before. If a make a new post I cannot find it as an entry in my new databases.
Please help!

Note: In my earlier installation I used the plugin polylang to setup my site bilingual. The plugin is still there but I have not activated it yet.