Honestly whilst everyone is recommending react/angular etc. I'd argue these are probably the worst places to start. It assumed a lot of up front knowledge and ability in web design.
Balaji has strongly suggested that they don't have a good grasp of the basics yet, HTML, CSS and vanilla JavaScript. Throwing out relatively advanced JS solutions does not solve this problem.
Balaji I'd recommend picking up some basic knowledge of HTML and CSS first - this will get you started building rudimentary websites and is essential knowledge for practically all web development. You must learn these before anything else.
Once you have some understanding of how these work take a basic course in JavaScript - which is what powers most of the modern web (through using HTML and CSS). If you start feeling comfortable with that I'd recommend looking up a framework, React, Angular and Vue are the normal recommendations. I'd personally go with React for the sole reason that it is - comparatively quite simple to pick up (once you understand JavaScript) and also very commonly used with strong community support.
In terms of turning this into an app down the road... Apps and web sites are not directly comparable. There are multiple ways of approaching converting a website into an app but most are relatively advanced. I would focus on what you are doing now before thinking about that journey.