Won't get bonus?

It says WarThunder Tasks give 25% more gems. I've completed the 1st Task but its not getting confirmed :/ So will I loose out on the Bonus or does it still count if they take longer to confirm?

What matters in the amount of gems it gives when the screenshot is accepted. Don't worry however, War Thunder always gives a lot. It often even gives 5000 in total.

So if I finish the task during the special offer but they take (up to 48h?) too long to accept it, I won't get the bonus? Meh :/

I've often been thinking about this post these last days, because things seem to not really happen like it did the last few months. I guess that's because it's the end of festivities. Now War Thunder isn't even the "Featured Game" anymore, making me fear for you that it might drop under the 4000 it is at (I don't think I ever saw it not featured during the time I've been on gamehag (8 months ?), although I only really checked the last ~3 months. And same for the reward, never saw it under 4000, but maybe it could happen now.
Anyway, I don't know if you've kept waiting for the reward to increase since the last time, but I'm thinking now I might actually be wiser to not wait :/ Unless, perhaps, if you're ready to wait for months. Most likely for a raise this summer. Else, around halloween / christmas. Knowing the drop affects most games, it should increase again at some point (Warframe is the only one that seems to be completely unaffected. Actually, its reward is even currently stable at an amount it stayed never for long before. Though its first task takes a lot of time to do, unless you have twitch prime. Although you can still speed things up a LOT by getting help from people. In short they can "taxi" you where you need to farm what you need, i.e. bring you somewhere you haven't unlocked yet. And the community in this game is clearly by far one of the best I've ever seen, so it shouldn't be hard to find someone to help you).

(hit the character limit, forced to split message)

As for your question, yes, if the offer is over before your screenshot is accepted, you will get the new amount. And yes, that s****. I'm not sure it's a good thing even for gamehag itself, because what this means is that it can be really fustrating for people, only contributing to them wanting to leave and stop using this site.
Even then, if the special offer ends before your screenshot is accepted because it took too long, it will still yield some frustration of course since you could otherwise have been able to complete several tasks with that special offer, that you couldn't only because of the time it took to accept it (if they accept it without you needing to get Misty to do it instead in the first place. Btw, do contact Misty anyway if it takes more than 48 hours, don't keep waiting)

And I've been writing a wee bit too much ^^' Or more than I anticipated, at least.