Your HTML and CSS experience is not enough to make a website at least that has a contact form. You need PHP with them, so if you do not intend to learn PHP, you will not be able to reach your goal without hiring a programmer/service (price starting from 30$, depending on the functions that will be provided by the site).
I disagree with that. Your HTML and CSS experience might just be enough to create a fully functional website. HTML and CSS are the basic tools that all web developers start with and you don't need anything fancy to create a simple website.
After all, this is how we all did it before the age of dynamic websites and fancy front-end libraries started.
Of course, if you want to deal with contact forms, you'll need some server-side programming as well. Any server-side programming language would do, not just PHP. You could also opt for a third-party service or a ready-made script that integrates easily into your website. As a quick and dirty solution, you could even use Google Forms connected to a Google Sheet.
All I want to say is that, depending on the type of website and its intent, contact forms aren't always necessary. Many businesses, for example, already use chatbots and live chat to communicate with their customers on their websites.
Respect your opinion, but OP has indicated that he wants a professional site, there are actually many ways without dealing with PHP, but whatever it is, programming is not that easy, know that </HTML> and CSS; is trivial, but when you want a "professional site" It turns out completely the opposite. Since OP wants a site for his project (not a personal site), He has said himself that he knows the basics of HTML and CSS which is not enough for "Pro website", then of course it is best to hire an expert, because this is a work, not a play.