Anime episodes differ form the manga

This might be a stupid question but did they put in filler episodes for the anime and not follow the manga completely.

That depends on what you understand for "filler". If it was to gain time, I highly doubt, since they weren't trying to follow the manga's pace. What the anime has is an entirely new mission at the end, taking place after the temple mission. It doesn't happen in the manga. The anime ends right after it.

Besides that, there are several other small differences, like character names, and the importance they give to the "Hinode station granny", making people think she has some sort of mystical connection with Gantz.