I've seen many people struggle to understand the tasks given, and so have decided to clarify it for everyone. As of the time of writing, I have finished 3/4 of the tasks, but there's a reason I haven't finished the final one despite having gotten well over 50 wins; the fourth task requires you to buy a dollar worth of premium currency. This and more will be discussed in further detail.
As for tasks, they're all fairly straight forward. For each, you must win a specified amount of games and will be rewarded with a specified amount of gems. For me, the tasks and rewards were:
1: Win 5 Battles for 1706 Gems
2: Win 10 Battles 1575 Gems
3: Win 20 Battles 2310 Gems
4: Win 22 Battles and get 150 Golden Eagles for 550 Gems
As is expected, the tasks take longer to complete the greater the reward- but you can fulfill these requirements sooner than it may first appear. Something I've heard little discussion of is how wins are calculated. Of course, in Warthunder knowing when you win or lose is easy, but there's a tip I'd like to share: you don't have to remain in the game until it ends- in fact, you don't even have to have lost all your planes. A simple strategy to quickly grind wins is to either rush the enemy planes or focus ground units until you're shot down. Once you've exited your plane and are prompted to select your next plane, simply return to the main menu. Although this usually results in completing the task quicker, your team being down a player can cause them to lose slightly more often, so finishing as many games as possible in a short amount of time is your best bet with this strategy. If you feel bad about playing this way, then I recommend you only play arcade battles, and that you only have one plane crewed while going into battle.
Next, we'll talk about submitting screenshots.
For the first two tasks, you should find no problem having them accepted. Simply take a screenshot of your full screen while under your account stats. You can find this page by clicking your name at the top of the screen, to the left of the large red "War Thunder" icon.
The third task will cause most people problems. Even though the task says nothing of rewards, you will likely have your screenshot rejected for the reason of "You need to get the reward and use it in game". This is an issue on Gamehag's site and you will need to have them reject it before contacting support. For those who might have an issue finding the support page, here's a link: https://gamehag.com/contact . As for the wording of your appeal, ensure you mention the game, task, and that you believe it was wrongfully rejected.
Finally, I'll offer my limited skill in the form of tips.
Test out using Q and E to rotate yourself on the yaw axis, allowing you to turn quicker on an enemy at the cost of verticality.
Shoot at the enemy in shorter bursts, only spraying if deemed necessary to combat jamming of guns.
Sometimes the automatic bullet leading is incorrect, as players often move spratically- try to learn the bullet travel time yourself
Sometimes a 1v1 is lost before it's over. In that situation, attempt to either down someone else or destroy ground units before crashing.
Stick together as much as possible. Pouncing on single enemies as a team near guarantees a win so long as you move quickly enough.
Well, I guess that's all I have to say about this. Hope you enjoyed reading!
Footnote, the image used as the thumbnail was from Warthunder's official site, and I do not claim to own any of it.