I am a beginner and have a question: do Germans use 'zu' or 'um +zu' with the verb 'gehen'? or they don't?

I presently understand that with 'gehen' these prepositions are not needed e.g. Er geht die Polizei rufen.
However recently I came across this sentence: Er geht in die Kneipe, um sich zu betrinken.
Why um+zu is used here if 'gehen' doesn't need it?
I understand that 'um+zu' gives information about 'why?'.......still I don't know why it's used here in above sentence if 'gehen' doesn't need it....can you help me understand this?
Thanks!

Question

I am a beginner and have a question: do Germans use 'zu' or 'um +zu' with the verb 'gehen'? or they don't?

I presently understand that with 'gehen' these prepositions are not needed e.g. Er geht die Polizei rufen.
However recently I came across this sentence: Er geht in die Kneipe, um sich zu betrinken.
Why um+zu is used here if 'gehen' doesn't need it? 
I understand that 'um+zu' gives information about 'why?'.......still I don't know why it's used here in above sentence if 'gehen' doesn't need it....can you help me understand this?
Thanks!

sopfia · Answer

@Rishi1 i recommend reading a chapter in "German grammar drills" about infinitive clauses, the book you can find online) it's all clearly explained there

mammamia123 · Answer

We use "zu" and gehen with an object and "um zu" to express the purpose of an action in a subordinate clause. Not only with the verb gehen. You can identify it mostly by the lenghth and the comma.
Er geht zur Polizei.
Er ruft die Polizei.
Er geht zur Polizei, um einen Diebstahl zu melden.
Er geht in die Kneipe, um sich zu betrinken.
Er trinkt, um zu vergessen.
Er geht einkaufen.
Er geht Milch kaufen.
Er geht in den Supermarkt, um Milch zu kaufen.
Er geht in die Apotheke, um ein Medikament zu kaufen.
Er kauft Blumen, um seiner Frau eine Freude zu machen.
Er fährt mit dem Fahrrad, um die Umwelt zu schonen.

carmii · Answer

The verb "gehen" is indeed a bit special. If you want to express, that you're leaving a certain place in order to do something at another place, you can often combine "gehen" with a second verb in its infinitive form.

einkaufen gehen
essen gehen
spazieren gehen
schwimmen gehen
schlafen gehen
...

Ich gehe morgen einkaufen.
I go shopping tomorrow.

Anna geht mit ihren Freunden schwimmen.
Anna goes swimming with her friends.

But this doesn't mean you can't form normal infinitive clauses with the verb "gehen".

Er geht in die Kneipe, um sich zu betrinken.
He goes to the pub in order to get drunk.