Question edited for clarity.
Do you mean the embroidery unit. If it is secondhand and has been stored for a long time, sewing machine oil, or worse WD40 goes 'gummy'. You would need to clean all the out. WD40 is a good solvent, so spray, leave it to soak, spray again and agitate with a brush. The wash it all off with hot soapy water. Dry thoroughly and after a few days, lubricate metal parts with sewing machine oil and any plastic parts with a dry silicone spray like Jigaloo. Test Jigaloo on a flat piece of plastic first as it is also a powerful fast drying solvent.
DON'T cut lumps out of your machine. There will be a sequence you use to remove the parts you need to access to the gears more easily. The Youtuber you referred to sounds like they have zero knowledge when it comes to these older style machines.
'Note' Some of the gear mount nuts are on a "Reverse" thread meaning you turn them the 'wrong' way to get them off.
My limited knowledge is more on the much older hand crank and treadle machines.
Try the Youtube link below for a channel called 'Andy Tube'. He has a good reputation for correct repair methods. The link is for a 758 but they're both Touch and Sew machines.
You could also try the Facebook group 'Vintage Singer Sewing Machines' as they have loads of knowledge about loads of different machines.
https://www.youtube.com/watch?v=zxd5hKjGBlE
Lois, all questions need full 'make model (what it is) please. Futura is a range of models so ''Singer Futura' isn't specific enough. Add the model number after the word 'Futura' and press enter.. You can also look for the Service Manual. There is one in the link, but no Error 20.
https://www.google.com/search?q=Singer+Futura+Error+20
..
Manuals Library (manualslib) is the best site for manuals by a country mile. I just opened this one in less than a second. the website www.manuals.is has it, but it is not a good viewing format.
Page 72 of the full manual may help, if you didn't have this manual when you bought your machine.
Hope this helps.
https://www.singer.com/search/support?title=5705
It is not uncommon for some Singer sewing machines to not have a model number. However, if you are still unsure about the authenticity of your Singer Inspiration sewing machine, you can contact Singer customer service for assistance. But the following link shows the number provided to the model. SINGER 4212' INSPIRATION ' Supra Enterprises Corp (suprasewingmachines.com)
