General Information:

We do not know where this takes place; it simply occurs one day when Jesus is teaching.

Now

This marks the beginning of a new event. (See: rc://en/ta/man/translate/writing-newevent)

This is an exaggeration to stress that there were very many of them. AT: "many tax collectors" (See: rc://en/ta/man/translate/figs-hyperbole)

"This man lets sinners into his presence" or "This man associates with sinners"

They were talking about Jesus.

The word "even" shows that they thought it was bad enough that Jesus allowed sinners to come to him, but it was worse that he would eat with them.