HELP! I don't understand trigonometry!!!

Hello,
I am Luciana Villanueva. I am writing because for a monograph that I must carry out for my school that has the IB program, I need to have certain knowledge about sinusoidals functions and waves, as well as the Fourier series and spectral decomposition. I tried to search this site but there was not the information I needed or it was very insufficient. Do you think it is possible that you can assign me or communicate with a teacher specialized in the topics. Since I was 9 years old I have turned to Khan Academy to improve academically, please don't leave me now!!!

PD. If it could be a spanish-speaking teacher, I would greatly appreciate it.