With all due respect kind sir, I can't decide that you are a bit stupid for this game or not.
For first part: Not entirely true. If you place double wire and mine on a totally clear path, of course it warns them that "hey there's a mine". But if you try to disguise it as an infantry blocker on narrow paths, it works.
For the second part: I don't know how you place or move your ATGs but if you let a T-70 rekt your raketen you are obviously doing something horribly wrong. I don't think that you need to be a genius to know that you MUST support your ATGs and not send them alone into everything. For example the Luchs can keep infantry at bay -> enemy sends T-70 -> raketen fires a shot -> tries to circle it -> Luchs will chop off it's HP. There's even an ingame tip that "hard counters are very effective but can be countered themselves."
+1
on urban maps kubel can sometimes be a liability with its poor pathing, so knowing when to do 2/3 volks + kubel vs 3/4 volks without can save you some manpower.
one trap a lot of people (cough... me) fall into is going mechanized and then building lots of light vehicles, which delays tech significantly. you can get around this a bit by having the special operations doctrine (so you can get cmd panther without having to build tier 4), but just watch out for it, especially if your light vehicle micro needs work (cough... me).