Hello there,
@ammara.
First: pick a language you really like and stick to learning it. You claim to have "learned" C++, Python, Java, HTML/CSS, and JS. However, have you really learned it if you have not mastered it? Have you really learned it if you have not made a half-decent attempt to apply it? It's the same with learning a real language: you need to go beyond the basics(common words/phrases), learn the advanced stuff(verbs, sentence order, asking questions, etc.), and combine all of the basic and advanced stuff together to be able to talk to and understand someone. That is how I see it: you haven't truly learned something if you cannot apply it, because it shows that you most likely do not understand it and do not know where in life it would come in handy(think of trigonometry: don't know where you would use it, but if you wanted to study architecture, you would be using it day in, day out - it's came in handy for then).
Once that's done, learn the essentials of the language. Using C, you would learn: variables and arrays, control statements and loops, functions, structures, pointers, memory allocation, file I/O, and even many parts of the C standard library. Stick to a path and learn as you walk along that path. When you learn something new, then follow some exercises or small projects which apply these in practice - this will help you to build up an understanding of it better and you'll get an idea of where to apply it on your own. You cannot learn without doing, because we humans are molded by experience. As another tip too: analyse the code of others - it'll help you get an idea of what makes "good code" and what makes "bad code".
After you have became somewhat decent with the language, just go and find a project. There are many lists online to help give you ideas, you can go on GitHub and search for projects to contribute to, or you could even take inspiration from a project or even fork it and ask yourself "what would make this better?" Just stuff like that to get you started.
In regards to your options, I would pick Python. It's an easy language that is very flexible and comes with many APIs, libraries and frameworks to help you build projects, a plethora of documentation and tutorials to help you learn, and a thriving support community to answer any questions you may have. Python can run on any computer and can do practically anything: automation, data grabbing, web servers, machine learning, data analysis, you name it. Swift is only limited to Apple devices and you pretty much need an Apple computer to be able to build apps with it(XCode). Flutter isn't a programming language either:
it's actually "an open-source UI software development kit" - that tells me it isn't really worth learning unless you want to get into designing portable and flexible UIs.
Hope this helps!