- Is the strict refund policy really necessary? Since you screen clients I'd expect you rarely (<1%) deliver a product the client hates. Perhaps a more traditional 'satisfaction guaranteed' would make the sale easier, and highlight your expertise. But I get that it introduces admin work.
- The portfolio is really nice, I'd find a way to break the format a bit to include a carousel of latest work. Could also be higher-up, the third message even.
- On mobile it switches the response bubble to the left?
- Consider centering the logo; adding some padding-top for mobile.
- It's not clear where you are doing business from, in the EU this can be helpful to know for tax reasons.
- Not having a contact-form in the style of a composing a message at the bottom feels like a missed opportunity!