I'm at the last mission of Chairon Base where I have to chase this pilot on the screenmap and then fight him? How do you catch him what plane do I use?

Use the XQU-2 Bee Fatty. As it's the only plane with the range to catch up with the latter enemy aces until you get the XF-0002.

How do you get that plane? I couldnt get him so I went on to this other campaign hopefully I will get better planes. I just couldnt shoot him enough in time.

If I recall correctly, the third ace is the MiG-1.44 MFI, right? Then in that case I'm not sure what problem you're having. The XQU-2, or just about any aircraft with a range of 5 or higher should be able to catch up with it. Unless you are trying to get the XF-0002, which is the fourth and final ace. In that case, I'd suggest only the XQU-2. If you don't have that, you're gonna have to gain some money and buy it from a particular airbase. (I forgeot which one. So you might have to take a look around.) I apologize if I'm not getting this right, but it's been a while since I've played the campaign.

Well I am now at the part where I have to destroy this convoy and its pretty had, i skipped that ace and when on to campaign 2 so I cant go back, but I'm gona have a look at an faq to see what plane is good for the convoy mission cuz I dont have any of the planes u mentions only all the ones I bought from all bases so far.