Altitude MSL is your altitude above sea level. Altitude AGL is your altitude above the ground. EG. at Denver, when on the ground your AGL will be close to/at 0 feet, but your MSL may be several thousands of feet.
Make sure to cross the threshold at 50 feet flying level to the horizon or no more than 2 degrees pitch up. Flying level in full landing configuration means you are flying at the correct speed for the type and weight of your aircraft.
Pull the nose up (no more than 5 degrees) until your VS decreases to VS - 200 to - 100, and allow the plane to touchdown. Cutting throttle to idle at about 10 feet helps.
Trim does absolutely nothing to help with landings. In IF, all it does is set your elevators to a new default position.
The horizontal line in your HUD with the - v- notch is your attitude indicator. The notch basically represents the nose of your aircraft. The fixed lines represent degrees of attitude up and down from horizontal. They are in increments of 5 degrees.
The little circle below that seems to move around a lot is your FPV (flight path vector), it tells you where you are going. When landing, you want to keep the FPV aimed at the start of the runway, and then the two big fat white aiming markers when they come visible.
My suggestion, always use the same weight (load) for all your landings, try 25%.
Learn to descend with your plane level to the horizon and/or no more than two degrees pitch up.
These will be your two constants for every landing.
Aim your FPV at the start of the runway. Don’t be afraid to crash or make mistakes, you learn a little something from each mistake.