Thanks Bernhard, I will read your writings. But I would specify that I have to do ALL Clementi's studies and ALL 24 Bach's preludi e fughe (12 from the first and 12 from the second volume). An other option is to attend to a 3 years university cours with less Clementi studies but with other subjects. Anyway, I must play fixed pieces. Unfortunately, music instruction in Italy is that!
This is a tall order!

(the Clementi is no big deal – just studies), but the complete book II of WTC?

You are in for a good ride.
I suggest you learn them in the following order (just a suggestion other people may have different orders – If so I would like to know):
1. no. 15 in G (Book II)
2. no. 20 in Am (Book II)
3. no. 21 in Bb (Book II)
4. no. 6 in Dm (Book II)
5. no. 19 in A (Book II)
6. no. 11 in F (Book II)
7. no. 2 in Cm (Book II)
8. no. 14 in F#m (Book II)
9. no. 7 in Eb (Book II)
10. no. 13 in F# (Book II)
11. no. 12 in Fm (Book II)
12. no. 1 in C (Book II)
13. no. 24 in Bm (Book II)
14. no. 10 in Em (Book II)
15. no. 5 in D (Book II)
16. no. 18 in G#m (Book II)
17. no. 9 in E (Book II)
18. no. 4 in C#m (Book II)
19. no. 3 in C# (Book II)
20. no. 8 in D#m (Book II)
21. no. 17 in Ab (Book II)
22. no. 22 in Bbm (Book II)
23. no. 16 in Gm (Book II)
24. no. 23 in B (Book II)
You may also want to go through these books:
Basic:
Eric Astschuller – Bachanalia – The essential listener’s guide to Bach’s Well tempered clavier (Little Brown)
Intermediate:
Ralph Kirkpatrick – Interpreting Bach’s Well-tempered clavier (Yale University Press).
Advanced:
Paul Badura-Skoda – Interpreting Bach at the keyboard (Oxford University Press)
Siglind Bruhn – JS Bach’s Well tempered clavier: In depth analysis and interpretation (4 volumes) (Mainer International Ltd)
You can read this book online here:
https://www-personal.umich.edu/~siglind/text.htmand this is an excellent site on the WTC:
https://jan.ucc.nau.edu/~tas3/wtc.htmlBest wishes,
Bernhard.