Déclaration revenus (tax declaration): need help desperately

Dear colleagues, I’m trying to fill in the form I got for demanding my numéro fiscal. I have to indicate “an estimation of my income for 2020”, as asked by SIP (Service des Impôts des Particuliers). My university (Sorbonne) is not helping me at all. The different people I asked about it (at DRH and the international research office) have no idea. I even don’t have my salart bulletin since December. Besides, I don't understand well the module SIP asked me to fill in :(((( Once I know which sum to put, where exactly should I put it? I would be very grateful for any idea and information. Merci d’avance! Riva