For starters, the north is much more open than the south and is better for MGs.
If your partner is going to go for a greedy build like mg, gren, sniper, you should team up and just play one half of the map together.
At 3:30 or so, you are really playing the game the penals want to play. Get out of those chokes and fight in the open at long range. Losing a gren this early hurts really bad, much more than for any other faction (besides maybe losing an infantry section).
At 4:30 you have 514 manpower and your ally has 366. Spend dat MP!
Personally, I don't think the stormtroopers are worth the cost unless you really need them for something immediately. Better to tech, a halftrack or a pgren squad would have more utility.
At 8:00 you lose 2 separate fights, one with a gren and one with an mg. Try to keep your forces together as ostheer.
Both you guys were too light on grens, thats why you lose the map just past 10 min in. At least one of you needs a blob of 3 grens that can move around the map (2 grens and a sniper would work too) and challenge the infantry sections and the penal battalions.
This one might be obvious but you should have moved that PIV ASAP, you should have lost it tbh and it was out of action for much longer than it needed to be.
Pushing too far with ostheer is very dangerous, you lose 2 squads at 15 min and at this point you're so far behind in infantry it's gonna be hard to win.
Double T3 is a waste, one of you go t4 and get a brummbar or a panther (depending on what you need).
Really nice play on the firefly at 19:30, well done. If you don't have infantry or pak cover though, its very risky to rush in like that. Your buddy loses the stug for basically no reason too. Both of you need to play safer with the vehicles if you don't have a way to scout. All things being equal ostheer will have a stronger late game with panthers and PIVs (and hopefully an elephant).
In summary:
Know which side of the map to play, in this case mid/north. Takes experience, I've made that mistake myself on this map.
More careful with infantry/make more infantry early. Fight at long range vs penals, close the gap vs infantry sections.
Keep your mg with your grens.
Don't double up on t3 and don't double up on tiger doctrines (one of you should have elephant).
The aggressive play is good, but make sure you have inf when you push, and try to find a way to look before you leap (as in, scout).
You guys had some good teamwork, use your voice comms more (if you are using them) and do more flanks/doubling of one side. Take advantage of being an AT!
Good luck in your future games