Regarding lesson 3 and building, especially rocket facilities.
Are they really usefull when you have von Braun? (costwise, if you lack scientists with rocketry or they skill is very low they are usefull, but it probably means that you are playing minor and do not have IC for rocket facilities).
Maybe it is my error but playing Germany I never bother with building them.
1st build could be justified since it gives 6 days reduction, however next ones give 2 days reduction (according to the Research page on wiki for tech difficulty 8 and skill 8).
Together (in HoI2) there are about 18 (+2 in 1936 tech) rocketry components +1 in assembly line (unless the time reduction works for other components of rocketry technologies), which gives you for the whole game "gain" of more or less 6*20 research days day for the 1st stage and 2*20 = 40 days for each next.
And von Braun has skill level 9 plus you will have extra modifiers (most probably -20% and more) from Computing technologies thus the actual gain will be smaller than 120 or 40 days.
Rocket facility takes 40 IC by 180 days. Which means that you can have 8 factories instead of 2 rocket sites. Which means that by the end of 1941 you will get 5 years*8=40IC years (about 14.5k IC).
And if you care about research time in rocketry (you do not need with German teams) and want to have say level 2 site, let us see: first important need for rocket technology is about 41 or 42 (unless you need to build V1) when it is time for turbojet planes. Turbojet engine is 1939 tech but you can not use it in 39. So IMHO you could start developing rocketry technologies in 1940 and would lose nothing. Which means that you can build 2 runs of rocket facilities starting in the middle of 1939. Which means that those 8 factories build in 1936 already gave you 16-20 IC years of production, and they are staying giving you IC and TC bonus.
Edit: I have noticed that on your picture rocket site costs only 20IC (in Hoi2 it was 40) so the IC gain would be halved.
EDIT:EDIT(a lot of them): I forgot to take into account those "secret" techs, they have another 20 rocket components doubling any research time gain. So it looks that I might be wrong. Anyway those techs are 42-43 or later techs thus first years could be devoted to IC development and only later (39?,40,41) into rocket sites development.