Onboarding Process for my first side project ever

I've always had the desire to build my own business, do more things I love and start in a way or another to contribute and build stuff. Although I'm a CS student I've never built anything from scratch and I am also new to everything related to business, marketing, customer-facing features, etc.

Today I decided to just start. I had an idea that went through my head for a week, so I started writing some todos in my new Trello board 🥰.

My first task was to write the MVP. I want to start small, so I choose some basic features for the beginning. The second step was to build the onboarding process.

I know that the first impression counts. But that wasn't the only reason I wanted to start with. I need some information from the user (like skills, experiences and so on) and I want to do this in the form of onboarding steps...
Something that look like the Duolingo app when a user sign up).

Now my first little challenge is: how to build a design for the onboarding process?

Are there any tools/products that you recommend? Although I want to use react on frontend, I think I would choose the other alternative if a part could be done in a better and more efficient way.