Your high ping with perhaps not perfect skills result in massive lossage.
The best way to train your skills is to play against a bit better players than yourself (some challenge, while still being fair enough so you don't get bored getting fragged all the time).
I would suggest playing regular DeathMatch first, as there are no extra things to take into consideration, just survival and fragging the others.
Some basic tips about FPS (quake1/quake2 etc):
- Use keyboard + mouse. There are some players who use keyboard only and really kick ass, but these cases are very rare (I've seen two keyboard only players). For right handed: mouse with right hand, and strafe left/right, move forward/backwards for the left hand. Usually ADWS or SFED keys are used. Other keys are bound to weapons or some other specials. Mouse is used to face the char: sideways turn, up/down for looking up/down (whether this is reversed is a matter of taste). Mouse1 attack, Mouse2 jump (jump need to be close at hand for rocketjumping). With 3 or more button mouse these extra buttons can be assigned some addional ops. Naturally these are just guidelines to give you an idea, you need to work out your own setup.
- Learn to run backwards and shoot your opponent following you. Yes, this needs some practice and you need to know the maps well.
- Keep your health/armor up, then you will always have advantage over respawning players.
- Don't use autoaim, this seriously mess up the aiming (no proper lead). Also learn to use slow weapons against moving target. Usually rockets should be fired on the gound (don't forget the lead!), this way missing rocket will still cause damage.
- Learn some basic routes to run thru maps (get weapons, ammo, heath/armor), don't just wander around without plan.
- Always keep moving, unless if invisible or otherwise in hiding. Sitting duck will get shot.
- When under fire, don't run straight lines or the opponent will have easy task figuring out the lead. Just try to run straight when the enemy has a rocketlauncher and you see what I mean.
There are tons of other stuff, but this is the most obvious stuff I could think of. :-)