Impossible Mission
 

Can anyone tell me how to complete the 36 pieces ?
I'm not able to solve the puzzle because I simply don't understand it...

Maybe this can help you.

tried it out - still don't understand it - my inventory is not the same as mentioned in the text...

Do you mean Impossible Mission 2?

The original was only released as a bonus with Impossible Mission 2025.

nope I meant the first part - where you have to put together 36 puzzle pieces which are coloured grey, green and yellow and have to build a word.

in the i.m.II you have to deal with music (melodies) as far as i know

You have to combine 4 pieces to get one punchcard and you need 8 of these punchcards to open the door to Elvins control room.
To put two pieces together they have to match by color and orientation. You can change both by moving a piece to one of the four 'working places' in the middle (via drag and drop) and pressing the corresponding button to flip it or to change it's color. If you think they could match you drag one piece above the other and drop it there. If they match, you get a new piece which is the combination of both, but if 'images can't overlap' appears you are wrong and you can probably throw them away by using the trashcan button.
After combining four pieces you should have a complete punchcard which is automatically removed from your screen and you get one letter of the password instead. Note, that the program will only accept the card if it has the right orientation (the color is not important), that means if you have a complete punchcard but it doesn't disappear, you have to flip it vertically and horizontally until it is accepted.
If you have problems to see which pieces match you can use the telephone to correct their orientation. To do this you have to press the top button on the left side (when I remember correctly) I think it shows 12 little buttons. Then the orientation of the two pieces shown in the 'memory browser' (dunno how to call it) on the left side will be corrected at the cost of 2 minutes, I guess. The pieces will then have a red mark next to them to show that their orientation has been corrected. If you do this for all pieces it should be easy to solve the puzzle. Later, with a little bit practice, you can also solve it without using the phone.
Have fun.