That’s your problem right there.
You paid money to get into a Tier and BR where the majority of the players have not played just 300, but literally thousands of hours, and thus have a very good understanding of the vehicles they use and they fight again, they know the ins and outs of the maps and the game mechanics.
As to SL, you win them by hitting, critting, killing the enemy, by killing AI targets, bases, by capping points, etc. etc. etc.
And you LOSE the silver lyons by repairing your vehicles and by buying ammo.
I fear right now you may be in aposition where as a beginner you barely survive, without killing or othewrwise earning a lot, and thus loose a lot on repair especially.
I can only recommend to take a few steps back, play the game from the beginning, to really learn how to best play it.
Also - often vastly underestimated - it does NOT mean that the higher you are in BR, the more fun you can have! You can have fun at every step, and fo myself I think for example with tanks I’ve had the most fun around BR 3.7 to maybe 5.7…