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But why does my tank feel like it's made out of paper mache, everytime it's normally a 1 shot kill on me. Either I blew up outright, or it knocks out my crew so all I can do is sit there and watch.
Also why is my middle tank gold? I hate that tank! All the armour is red to it!
I can only seem to get crew 3 to research.
Ok let me try and answer your points:
This game tries to be more realistic so if you shoot in the right place with the right ammo you can potentially 1 shot any tank all the way from the lowest tank to the best tanks (ammo rack, crew compartment etc). That being said low tier tanks like in your screenshot are all basically paper mache machines which mirrors how things were at the time/outbreak of the war. As you go up through the ranks certain tanks will start to become better armoured.
The gold tank is a premium vehicle so it earns more money and more experience.
This game is different to others, you don't want to skip down lines of tanks you need to keep a line-up of tanks that compliment each other rather than focusing on a single one. So for example in your screenshot above you should try and find another tank for the middle "choose vehicle" slot that is also 1.0 (like the gold tank) so you can choose from 4 tanks in battle. You can expand to a 5th if you want to pay the 50,000 too (if you have something researched to use the slot that is).
If you switch from Arcade to Realistic, you could also chose a plane for one of your crew slots instead of having 4 tanks you could have 3 tanks and 1 plane etc.