Missing texts, buttons display elements from admin after upgraded from 2 to latest 3 version

Hello everyone,
I've upgraded the shop from opencart 2 to 3 by following the upgrade documentation and I have to major issues:
1. After the upgrade on my shop I have some text missing translations, buttons and on the catalog the product are now showing up(can the attachments screenshots).
2. When I try to access the store the follwing warning is showing Warning: Undefined array key "arabic" in /home/.../catalog/controller/startup/startup.php on line 117Warning: Trying to access array offset on value of type null in /home/.../catalog/controller/startup/startup.php on line 117Error: A theme has not been assigned to this store!
I've removed all languages and keep only en-gb but nothing changed.

Someone else had the same issue in the past or know where I can check it?

Thank you.

Did you update your language packs to versions compatible with OpenCart 3.x?