I haven't advanced any further than the first south-western island. I just can't match enemy's production rate, that is the problem.

The Mech doesn't help much either.

Edit: It's mission for the Evolved, I forgot to mention.

Was that a map where you have a base or no? I can't really remember.

WIth KKND Xtreme, the tactics are the same regardless of faction and map (except for maps where you don't have a base). Get oil, find out where your enemies are coming from, put enough static defense structures there to hold them off, build up your tech and your army, when ready wait for the enemies next attack, then attack them when they are on the run. Might have to do a bit of manouvering when you're ready to move out but that's pretty much it.

WIth KKND Xtreme, the biggest challenge is holding your base. Once you've got those static defense structures up, you're already halfway to the finish line.

You have a base, but you start at the north-west, your base is at the south-west, you have to get to it first. Indeed holding the base is a big challenge here, unlike previous missions. Enemy is attacking with T4 vehicles from 3 ways.
I'll try to use defensive structures, thanks for advice!

Hello, i have other problem with this mission, i managed to beat enemy base and destroy all of his buildings and units but the mission will not end. Only occasionally there comes the attack from north (where the mecha was held). Do i have to endure some amount of these attacks? There is nothing blue on the map, yet the mission will not end.

tried to restart mission but even after completing it for the 2nd time it won't end

OP surely isn't looking for a solution anymore but I just played the mission several days ago, it's indeed one of the toughest ones in the game because there's only that one rig you can safely use right away, and it's past a bridge and you can't build a power station right next to it. Anyway, the thing I did was upgrading the blacksmith ASAP so I could build additional tankers, at least five, to achieve good income. Then I kept my main force between the oil rig and the bridge, the narrow bridge gives you a minor tactical advantage with enemies passing it one by one. I managed to survive several attacks and build up a slightly larger force. Then I sent several units South and destroyed the turret there, from there I passed the Southern bridge and destroyed the oil rig there and soon after all enemy tankers which pass the area to the East.. Using the bridges to my advantage I was able to survive despite the enemy having more resources and a larger force.

Another important thing: right after you start the mission, before sending your troops to the base to the South go East. You will find a bunker there, if you get close with one of your units you will receive a comparably powerful mech which will help you a lot early on. Sadly you can't repair it but it should still survive a couple of attacks.