This is an EMA (Ecole Mathematique Africaine) School of CIMPA. This hybrid School is nominally based at the ICTP-East African Institute for Fundamental Research [EAIFR] in Kigali, Rwanda; it will offer students concrete and effective mathematical tools from algebra, group theory and geometry that can be applied to any scientific field. Consisting of 8 working days 12-15 August and 17-20 August, with one rest day the 2+2 courses shall be running concurrently. Lectures will be given remotely by video link.