It's a very broad question because this depends on the industry, where your audience is, their demographics, etc. But I think a general answer would be word of mouth. If it is your product, start hitting events and visiting potential customers, offer them a 5 minutes presentation on why they need to use your product. Make that all day every day and you will get your firsts users and your first feedback to improve

Usually, already built solutions offer a process that you have to follow in order to use them. In other words, you don't adapt them to your processes, you adapt your processes to the tool. If you are a new company and are low on cash, use the solution. And when you start making money you invest in your custom platform, unless your new company is based on your software product.

Sure, send me your website and i can give you a Feedback. You can also use Google PageSpeed Insights and Google Lighthouse, when you send me the website, make sure to explain what's the goal of the website, Awareness, Leads, Sign In, Sign into a newsletter, etc

Actually what it would be useful to you is a Product Owner, or Technical Producto Owner to help you design your MVP (Minimum Valuable Product). The MVP would be the first iteration of your project, and it would help you validate your hypothesis about the value and market of your product. A developer is a good profile for this job, but at least with 5-7 years with experience in mobile apps and web apps. I also recommend coaching with some CTO of a similar company or somebody who has been a succesful CTO for ask her or his opinion.

I am Software Developer for almost 10 years now, i will continue doing it i think for the rest of my life. I've been almost 6 years now as CTO of a Software Factory developing Technological Products, and i have a lot experience in the subject that you are referring. You need a studio that understand your product, and take the time to understand what the idea is about, ideally with severals people from the Technical side who can understand a Product Process and how it can be matched with your product. That has to be your main goal, and not the Developers. A product is build as a solution to a necessity, and developers usually do not understand that. Also your provider has to have compliance with the most advanced techniques in Product Development (Agile, Iterative Increments, Change risks), and be available to manage the Development Team in that way. Developer teams is an underlying issue, that can be solved with money and that's it. A Team of 3 Developers, with a Product Owner and Coaching (Scrum) could cost between $10.000 and $70.000 a month depending in which country you hired. And do not get yourself fool by golden salesman, a Software MVP must be out in two or three months tops, and be ready for retrospective and adjustment in the course for getting to optimal response to the market and strategical changes.