Give it a rest for now. You can always correct your high school diploma or add new items. Do not start your studies, because it will not help you, I know a lot of pseudo IT specialists who have not even known what to do with themselves for several years. Later, everyone thinks that there is no job after graduation. It is, but only after specific high-level studies, because there you must have knowledge.
Mathematics helps in solving many problems with algorithms, as well as logic.
Without this elementary knowledge, a person struggles with difficulties, yes, you will program, because you will learn in practice over time, but there will always be something missing.
The extramural studies (in a good polytechnic university) are of the same level as in full-time studies at the same university, with the difference that during the day studies, many simply waste their time having fun. (unfortunately, you also need to have high school-leaving exams, even for extramural). At weaker universities, studying at all looks funny ...
Besides, do not look too much at the points you obtained at the high school final exams, because it is cabaret and not high school exams, a, b, c, d? these are some balls; / ... but these balls you have to go through because we have such a goofy system. You just need to know and improve yourself, not to compete with others.
And again ... mathematics is a tool without which nothing can be done in many areas and in electronics or computer science it is the primary element, vocational subjects are just an addition.
You will understand math - you will understand the rest. And do not stress, think calmly and follow it.
