Words can have different meaning depending on context.
Da = from / by / to / for / since / on /
questa = this
parte = part / piece / side / way
prego = you are welcome / please! / after you! /
A word by word translation could be something like:
Da, questa, parte, prego.
To, this . . . , part , please. ~ This way please.
Yeah, but how's a beginner to determine the context and the corresponding answer from one sentence?
"Prego" is commonly used when you are asking/offering someone to "please" do something or take something for themselves (i.e., it benefits them).
"Per favore" is used when you are asking someone to "please" do something for (or give something to) you.
For example, you would say "prego" if you were asking someone to "please" sit down to the dinner table, or you are offering them some pasta.
You would use "per favore" if you are all sitting at the table and want to ask someone to "please" pass the pasta to you.
In this sentence, the person is asking someone to "come/walk walk way", so "prego" would frequently be used instead of per favore. I'm not a native speaker, but this is what I've observed whenever I visit Italy.
It is correct I think, based on usage provided in Reverso Context, however I am guessing that this is a commonly used expression so they haven't thought of allowing other valid translations. http://context.reverso.net/traduction/italien-anglais/da+questa+parte
It is, yes! Look at https://www.thoughtco.com/italian-preposition-da-p2-2011458 and https://www.thoughtco.com/italian-preposition-da-4098161 for some explanation.
Yep! It's confusing, but here are a couple of articles to help: