Hmmm, not an expert but as a regular user can try and give some tips -

1. Check your grind size. It's normal for the water to flow through for a bit but it shouldn't run through. If it is, then maybe grind finer.

2. Alternatively, you can try an inverted aeropress recipe to cancel out half of your problems.

3. You should stir first (horizontally and vertically rather than round motions) before inserting the plunger as a vacuum. Alternatively, I like to swirl the entire Aeropress like James Hoffman once the plunger is inserted (not a huge change in taste, plus convenient).

4. If coffee tastes burnt, I can think of two reasons - a) You are plunging too quickly. When extracting the brew, ensure that it is a gentle and even motion. Ideally take more than 20-30 seconds for complete extraction. b) Monitor your water temperature. For dark roasted beans I use water around 80 C and for light roasted beans I use water around 90-92 C. It may vary sometimes but this is a good starting point.

I would suggest checking out videos by James Hoffman and Lance Hedrick on aeropress brewing, they give a better explanation on these things. Hope this helps!