Part0:
and used the 'old bootloader' option as you suggested to upload my sketch while selecting the Nano board.
sterretje:
You will have to upgrade the board manager to version 1.6.21 (at the time of writing this, higher versions have a bug). You can use the 328P option once you have upgraded the board manager.
I did not tell you to use the 'old boot loader' in your scenario; see above. I only referred to 'old boot loader' in the below
sterretje:
Board manager 1.6.21 will also give you the above mentioned 'old bootloader' option that you can use for older genuine Nanos and for clones.