Protect my site from SQL Injection, XSS and more

I have a simple PHP/MySQL site that will launch soon. I would like it guarded against simple attacks. User input is a contact form and a Stripe payments form. Tell me in your proposal what you can do for my site. I've included some files to give a rough idea/starting point. The cost you propose should be final, including all work you mention. At a minimum, work to protect from SQL injection and cross-site scripting (XSS) should be included. I'd ideally like my htaccess file to be looked at and improved, if possible. If you can include Content Security Policy, that's a bonus. I do not expect 10+ hours of work for this. I just want the basics covered so my site is at less risk/not such an easy target. If you can do what I've asked in a couple of hours or less, price your proposal accordingly. I will only award this project to someone with a proposal that demonstrates what you can do within the budget range.