Welcome to the club, Nabeel.
You do realise that you might be making a mistake? Writing is addictive. It can take up huge amounts of your time, even when you're not actively writing your head will either be in a story or noticing things that seem to be a part of a story (because everything is). It rarely pays well, if anything at all. You'll rarely be completely satisfied. But you will do it anyway ... because when it's working there is nothing else quite like it.
I've said that I don't plan my writing, but that's a simplification of the truth. I start with, as you describe it, snapshots or video clips in my head. At this point I know nothing about the story. For me, the only way forward has been to write those images, to immerse myself in the scenes so that I can meet the characters and see what they're like. With that done, I step back and try and work out what it means; who are these people, why are they here, how did they get there and where are they going. I still tend to avoid detailed planning, but after a while I know where things are headed and so I try to work out what should happen next, and next and next.
Creating natural sounding dialogue is difficult. One of the problems is that normal/real conversations aren't suitable for narratives. People waffle on a lot (just look at how much I've written already
). If you think about it too much you just become self-conscious and get nowhere. My best advice is to read a lot. Find authors that do it well, Stephen King springs to mind, he's an author that manages to impart a lot of information about his characters through the dialogue.
And dialogue is important. It's too easy to fall into passive story telling when you avoid dialogue. Dialogue helps to force you into the imperative. From the reader's perspective it helps to break up the writing and to set the mood of the scene as well as the characters.
A while ago I wrote a short story (3300 words) that was entirely dialogue. No descriptions, not even any attributions. It was told as a series of interviews (I pretended I was listening to a radio). While I haven't had the time to clean it up enough for publication yet, I'm very pleased with the result. It helped to prove to me how much you can describe your characters just through what they say and how they say it, and to demonstrate that it was possible to avoid all those bumbling "he said", "she said" attributions that so often distract. Since you're in the mood for experimenting, you might try something like this, it's interesting.
As for getting friends to review ... I had the same trouble. Lots of nice things said, but not much in the way of helpful criticism (eg: what bits
didn't work). The thing to remember here is that only writers and editors look at writing
that way. Most people just read, they read what's there on the page and accept it, they rarely analyse. So unless it's completely appalling the reaction tends to be positive. Yes, some will pick up the occasional bit of grammar and spelling, but that's not important yet (not until final proof-reading before publication). This is where your writing group is likely to be the most help, working with others who know what you need.
One common, but good, piece of advice is: when you first finish a story, put it away for a while and try not to think about it. Come back in a few weeks or months and go over it again. When you come back you can ask yourself: Does it still work? Which bits need to be cut? The extra distance from it really does help.
Also, remember that not everything you write has to be published. Some things don't work. They were still worth writing, I find I have to get things out of my system, but some stuff just doesn't work out as you'd hoped. It's all practice. Move on to the next.
ETA: Will you look at that! So much waffle, you'd think I knew what I was talking about. Bear in mind that all such advice is just one person's experience/opinion ... it's worth about what you paid for it. 