Learn English – Use of place prepositions

Yup - those prepositions are redundant. The short answer is that you're right and should follow oerkelens's advice.

Background in case you're curious:

One of the grammar rules that is drilled into the heads of many native speakers of American English in grade school is along the lines of: "IF YOU END A SENTENCE WITH A PREPOSITION, THE WORLD WILL EXPLODE AND ALL THE KITTENS WILL DIE". Many people learn the "to which" construction as a way to get around that.

• "Identifies the vendor which the port speed is associated with." ENGLISH TEACHER SAYS NO!
• "Identifies the vendor to which the port speed is associated." English teacher says yes!

But what happens in some cases is that the native speaker comes to sort of understand "to which" as its own relative pronoun, instead of a relative pronoun in a prepositional phrase. In that case, they perceive that their sentence still needs a preposition, so the "with" is tacked on at the end. That makes sense, because if you reorganized the sentence, you'd say "The milestone is associated with the vendor" - so "associated with" just kind of runs together nicely in the brain. It's understandable that the writer would want to tack on a "with" after "associated" since they appear together so frequently in other sentences.

This is the result of one of the longest and hardest-fought prescriptivism vs. descriptivism (PvD) battles in English. In my opinion what happens is this:

• The prescriptivists rail so hard against ending a sentence with a preposition that...
• ...regular speakers (who don't care about the PvD fight even a tiny bit) end up inventing something that makes sense to them, leaving...
  • ...the descriptivists scratching their heads about where on earth this came from, and...
  • ...people trying to learn English scratching their heads even harder about why everyone is writing incorrect sentences all the time.

This is impressive to me.

is the usual way to say what I think you mean (more specific context would be helpful).
See to:

6. preposition
   You use to to indicate who or what an action or a feeling is directed towards.

Meaning as you see "this", or the concept of "this" comes to you, it is (not) impressive.

As for:

This is not impressive for me.

The only related definition I could find was for:

5. preposition
   If you feel a particular emotion for someone, you feel it on their behalf.

Meaning my feeling is that it is (not) impressive. But in your example doesn't make a lot of literal sense. In the same sense, you could say something like:

I went out with her a few times, but she was not a good match for me.