Profile of Sorang

My agrens couldn't fight well against enemy infantries with BAR rifle.
I got 2 scout cars(222mm) but they got bazookas so I couldn't do it's job.
I think the strongest point of my strategy is when I'm pumping out Stug-Es,
but Stug-Es were destroyed easily by enemy infantires and tank destroyer. (The enemy had picked armor company commander)
After I lost a bunch of stug-es and scout cars, I could do nothing against those enemy infantries and tanks.

Hello!
I have some questions.
Maybe some of them have already been asked and been answered before, so you might say 'Search it on the forum before you make a new topic'. But since my main language isn't english, I have many issues at searching for the informations.
so don't get upset too much. I'll remove some of the questions if they have been answered in the past.

I've played warhammer 40k series and coh1 so I know how the systems work. (covers, commander skills, etc)
but I don't know much about the strategies and the builds.
Some people have told me I should pick wehrmacht and mechanized assault doctrine.
This is the strategy i've used
　I start with 2 AGrens and 2 MGs, 1 Pioneer.
　I build tier 2, get 222 car. and pak if I need one
　Get a tons of Stug-Es, Be happy
　Tier 4, get the car with a rocket launchers (I don't remember the name...) or Panther
The strategy have worked perfectly in most of the games.
but as time goes on, I started to keep lose.
AGrens were hard to control. they die too easily. I'm scared of soviet's flame grenade(or something)
If they even have mortar teams and MGs. My infantries do nothing but dying in early game.
on that situation, evenif I have 222car, the car can do nothing because infantries can't support the car.
If the car is alone, it would be destroyed. I surrender, deciding not to play this game never again, get sad, cry alone, and kill myself.

I don't want to kill myself or get sad
so I think I need to learn more strategies. I tried to watch some replays, but since I'm just a noob, It's hard to figure out what's going on by watching replays.
Somebody give me a simple explanation for new startegy or tips for the strategy that I've used? Help...

.
The reason why I've tired wehrmacht only was just because wehrmacht is the only faction that I learnd a strategy.
I know nothing about other factions. I wish I could play OKW because I used to play as panzerelite on coh1.
but I can't find any guides for them. even on this website, on the guide page, there are only a few guides.
so would you recommand me a basic opening build for other factions as well? or link other topic where I can find them... I've tried to find it on my own but I couldn't because my english isn't good, and some topics were about past game. I mean, the game has been changing. For example, some topics are talking about when you still could get panzergranadiers on tier 0. It's hard for noob to distinguish those past informations from current inforamtions...

T_T
If the questions are way to common or if I broke any forum rules
just let me know. I'll delete the topic ASAP...