Swift vs Angreifen - Where did I go wrong?

So being rank 5000/4000 as Soviets and having only about 380 hours in the game this was a complete surprise. I checked afterwards and indeed I was matched up against the real Angreifen.

I wasn't feeling too confident knowing who I was against but nevertheless I played on. The first seven minutes of the game were definitely my strongest where map control fell into my hands reasonably easy. A lot of my problems emerged when I started to accumulate mistakes, not flanking the cut-off with conscripts to avoid the MG42, failing to put units behind cover because I was misclicking the one next to it, accidentally box selecting multiple units that I wanted to maneuver, dodgy mine placements (except for one of them) etc.

Watching it back I noticed that in engagements I was generally outgunned and this contributed to the shift of map control away from me, as well as the sneaky S mine field so carefully laid down outside my base approach lanes.

So my questions are what else did I do wrong, and how can this be overcome?

And well played to Angreifen as well, I'm not rage-posting because I felt I lost unfairly or something.