New and confused

Lert: My guides explain basic game mechanics. As for your other questions ...   - When you are bottom tier your job isn't to brawl their high tier tanks, but to annoy them. Flank them, attack from unexpected angles, know weak spots. Another part of your job is to prevent the enemy's low tier tanks from doing that to your high tiers.
  - Damage earns credits. Learn weak spots, make sure your fire is effective, and only fire premium shells (APCR, HEAT) when you need to. Finally, try to survive longer.   - WN8 is a third party metric that tries to measure skill. At your experience you needn't worry about that yet.