how to put cheats? (Area 51)

Life - float number, from 0 to 100
Mutagen - float number, from zero to 100
Cartridges in clip - int.

You can patch the memory manually, you can take CheatEngine and make an injection through an autogenerator (it's faster and easier)

Lives:
A51.exe+FA86E - subss xmm0,[esi+000000BC] ; <---- Here we are being taken lives, you can replace this string with nop, for example
A51.exe+FA876 - comiss xmm1,xmm0
A51.exe+FA879 - movss [esi+000000B4],xmm0

Cartridges in clip
A51.exe+6FA8B - sub ebx,edx ; <--- here they are taken away from us
A51.exe+6FA8D - mov [eax],ebx

You can just sub, ebx, edx - again, replace with nop
The value not in the clip can be negative, but this does not play any role

Mutagen
A51.exe+4C1FE - comiss xmm1,xmm0 ; <--- it's a long time to explain here, after tracing, if everything will be clear and so clear
A51.exe + 4C201 - ja A51.exe + 4C206

Here we stupidly kill these 2 lines

I did not look for grenades.

PS NONE of the trainers that are available on the PG, with the Russian version of the game * (1.1.0089007e) do not work. So I had to do a little research.
So it goes.