Well... some of this, such as knowing where to begin or getting mixed up, as well as knowing how or where to start, I think are things only you can figure out for yourself. As far as how to word what you want to write I think that's also something you just have to figure out as you go along. (Reading & replying to other members' posts can help with some of that by showing you how they're doing it.)

One benefit, here on PC, is that you can always preview your posts before you post them. In fact, you can do that multiple times if you need / want to. And you can even edit what you've written, for a period of time, after you've posted it. You can even delete it altogether, for a period of time, after you've posted it. So there are lots of opportunities to make changes or even change your mind altogether.

As far as upsetting another member, here on PC, I personally wouldn't worry too much about that. Just always strive to be respectful & supportive. And then there's always the trigger icon you can use. (It's brown with a black X through it.) There's also the trigger box you can use to not show something you think might be triggering for other members so they can choose to open the box or not as they see fit.

Another option for you, if you're uncertain as to what forum to post in on a particular subject, is to Personal Message a Moderator of the forum you think you'd like to post in to make sure your topic is appropriate for that forum. Lots of different options.

So my personal advice would be simply dive in here & continue posting. As the old saying goes: "It all comes out in the wash." I see you're actually a 1+ year member & you have 3 posts to your credit already. So it appears you're off to a pretty-good start. The answer to a lot of your questions, I think personally, is to simply keep posting. And, with time & practice, it will all fall into place. I know the forums, here on PC, can seem a bit intimidating at first. But it's a good place. And (most of the members at least)... don't bite!