I´m really counfused about the word "gazetelere". I know that "-ler" is a suffix for the plural form, but where the "e" comes from? Please help me.

You are correct that lar/ler is the plural suffix, and added after that -

e/a is the dative suffix, indicating movement towards or to ´the papers´

de/da is locative, indicating in/on/at

den/dan is ablative, indicating from or movement away from

Thank you very much, now it´s very clear to me