How do I turn an idea into something tangible?

1. Do you want to run a business? or
2. Do you just want to develop your idea into a product/app?

For No #1, you don't really need to learn backend skills or anything. You already have an idea, you have frontend skills which means you can create a prototype on your own. Come up with a prototype, show it to potential investors/customers/partners and gather their feedbacks. Then decide what to do next.

Answer for No #2, then yea learn a backend skill. But I still think you should come up with a prototype while you are learning. You can do a lot with a prototype. Once you are satisfied with your prototype version then develop the actual project.

Just my 2 cents.

Edit: there are also various website builder solutions (wix, squarespace, shopify, wordpress, etc) If your answer is No #1, you might want to research those. They might be cheaper and faster than hiring someone.