Wordpress Database Fix Needed

We have a issue writing to the Wordpress database. 1. When you try to write to the database, it give a Error. 2. You can't customize the Theme. When you try to save it to the database it give an error. 3. When you add a new User to the website, it does save the user to the database. I am using Hostringer. com. Give me a quote. I want a flat fee.