That mathematics is not a compulsory spécialité is the structural feature that changes outcomes most in the French system. A student can leave the Baccalaureate with very little mathematics.
Three separate places
The first is spécialité mathematics: the fullest option and, when carried into terminale, the heaviest. The second is the option level; both the complementary course available when the spécialité is dropped and the advanced course added on top of the spécialité sit here. The third is the scientific literacy level inside the tronc commun.
The three differ in depth, and higher education programmes state which level they expect on their own pages.
The consequence of the decision
Engineering schools and quantitative programmes expect the spécialité level. The complementary level may be sufficient for some programmes, and that is read programme by programme.
A student who drops spécialité mathematics at the end of première has closed some higher education doors two years in advance, and that is invisible at the moment of the decision.
The advanced option
A student continuing spécialité mathematics can add a further advanced course. That is becoming an expected signal for applicants to mathematics intensive programmes.
The load is real, though, and if it lowers the term grades of other subjects it works against the student through contrôle continu.
The form of the content
The exam consists of long problems divided into parts. Each part rests on the result of the previous one and reasoning has to be written out.
An answer that finds the correct result without writing the reasoning does not earn full marks. That is where students coming from the curriculum in Turkey lose most.
How to study
Revise topics only where a real gap exists. Then work long problems in exam format and write the justification for every step.
Méthodologie is a separate heading: how a proof is constructed and which phrasing earns the mark. That is studied independently of subject knowledge.