1) Download savegame file

https://drive.google.com/drive/folders/1vA-ohpRdeYFSev-XLbmJjO6mlo4l5OkC?usp=sharing

It has two files, one with difficulty called Survivor Stalker Hard with a good ending (can be bad if you don't shoot the machine at the end).

2) Find Metro 2033 Redux save file location - you have to delve into your Documents folder to get your hands on the 4A Games folder, which contains Metro 2033 Redux.

3) C:\Users\YOURpcNAME\Documents\4A Games\Metro 2033\SomeWeirdNumbers
... with YOURpcNAME being your Windows Username

4) Your YOURpcNAME will be different, so just make your way to the Windows Users folder and figure out which profile is yours.

5) From there, seek out the weird numbers folder. BEST THING to do is to erase what's inside the Metro2033 folder and paste my contents.

5a) You can always change your own save game by adding '-copy', just to keep it for later, in case you need it.

6) Now you have to erase what steam keeps in the 'cloud', so your save won't be simply downloaded again. You need to head to:
Steam -> Library -> Right click on Metro2033 Redux -> Properties -> cloud
erase the save there

7) Now you should have my copy of a whole folder and it's ready to be played!

8) Run the game and enjoy! (you might need to play the endings via chapter select to unlock all)
9) If you want your own save back, just erase contents and copy your old save and run the game -> done!