right against double jeopardy???

can someone tell me what to do im only a pre-law student. one of the member of our family was filed a case for estafa(criminal case) he has been brought to trial previously. he has a legal documents pertaining the case. he was convicted not guilty orally by the prosecutor "i think"(he does not tell me the process or anything about the case) that's what my mom told me. i believe so that the case was disposed or terminated.

Now here comes the problem, the complainant filed a case again with the same complaint. but now the prosecutor is different from the 1st case. (i believe that the complainant made an agreement with the prosecutor "under the table" for them to succeed with their intentions and also i probably think that there's a new process of law ongoing. Now he is in the regional trial court. i cant understand that person because he doesnt tell me anything and i cant ask him because my mom told me not to ask because it will hurt his feelings even in a nice and decent way of asking.

Question:
can the accused depend with the constitutional provision written in the title of this message?

can he file a case against the complainant?

what are the things that i am missing in this situation?

hope to hear from you guys. thank you so much.