Have your papers been confiscated or do you have them? Are you allowed to go abroad/travel? Do you have a passport?
Yemeni’s situation in Saudi Arabia is similar to segregation in the 1950s, so your first order of priority should be to find a country that won’t mistreat you thus.
Obviously you cant return to Yemen since it’s being bombed to ruins.
Tunisia or Lebanon may be your best bets. UAE might be a closer solution but not sure you’d be “free”. Look for countries with strong adult education, continuing education, etc. You need to get a "real"HS diploma. A possibility would be to investigate online IGCSE’s. You’d need to earn 8 - you can take some subjects you already know, like English, Geography, History, and even Ethics through Islam (it’d probably be a very interesting subject for you actually, as Islam is seen as a subject, and not a dogma, a matter of knowledge to be discussed not a truth to be believed) and catch up on science: core math + core science + ICT + statistics would cover the basics in STEM fields. IGCSE’s are considred sufficient for some universities, but most require 3 A-Levels afterwards (or AICE).