@Qeria
You are probably using an ACP custom theme. You can try this if you have access to your php myadmin in your server.
1. Open the core_themes table
2. Write down the ID number of the theme by default, IPS (from set_id column)
3. Open the core_members table, on your profile row in the skin column, change the theme number to the theme number that I wrote you to remember above. Save it.
4. Delete cookies and cache from your browser and then load your site and login. Try and log in to ACP, then clear site cache.
