We have a VERY good game here with the unique opportunity to try your best to manage the Soviet Union. Of course, what is difficult is to make the right choice when the phone is ringing about a particular problems and it's even harder to manage the "policies" and "budget"--"by details" buttons. There is no manual ( it would be helpful, I didn't knew I could save your game and how ) but it would help a lot if there was one.

How can we find the right value for the money in the savegame even whit a
hex editor it's dificult

Or use Cheat Engine or Poke.

I don't think it will work for such old game

It will. All games use your RAM, and if they do then their memory space can be altered no matter how much kb or MB they take up.
It also works for games running in emulators, eg DOSBox.

I did try but it didn't work.

Then you were doing something wrong.

Run the game in DOSBox.
Open up Cheat Engine and choose DOSBox as the process to work on.

Choose First search. The money is most likely stored as an 8 byte value.

Do some stuff in the game as long as it doesn't change your money. In CE, choose "unchanged value", then "next scan".
Repeat this process a few times.

Do something that lowers the money. In CE, choose "decreased value" then "next scan".
Repeat this several times as well.

Finally, do something that increases the money. In CE, choose "increased value", then "next scan".

After a few repeats, you should have a very small list of offsets to choose from - ideally only one.

Double-click that offset on the search list to make it appear in the bottom list. You can change its value or freeze it to make it unmodifiable by the game.

Ok,here's a mini-walkthrough.Play as the nationalists, and keep the starting policies intact. Use the money from economic growth on agriculture,raw materials, transport, and industry.
Use your residual funds and try to get environment to around 100, increase the leisure funds to keep the people happy.
Increase both civil and space r and d to around 50-70 and increase it if you have the money.
Every year use,the money you gain on these things, and your gnp will grow by around 400 a year. The r and d is for bonuses you get from new discoveries.Just continue this, and you're all set!

I've tried and failed myself. Did you follow the instructions too?

Did you set the search for "unknown initial value"?