Dear Sir or Madam (przecinek)
I was in your youth hostel, 'where you are the owner' (nie wiem po co to jest - jak jest 'ich' hostel - to kto inny moze byc owner?) two weeks ago. I think that you MIGHT remember me. (might- dlatego ze 'moga' pamietac, ale nie jest gwarantowane ze musza)
I 'choose' (popraw) your hostel, because it 'is' (WAS - bo akcja dziala sie wczesniej) located in the mountains and there is beautiful view of the nearby village. 'Farther' (further), I was very glad that I 'can' (could) breathe the fresh air. 'Altough' (ortog), the views and air was great I 'do' (did not) not have (a przedimek?) strength to trek mountain trails. The hostel guests organized (przedimek) party each night. 'There' (zle tutaj masz na mysli, 'one') 'was' (jak parties byly kazdego dnia to znaczy ze itu ma byc l. mnoga) very loud which I really did not like.
Meals 'on' IN- the canteen were cold and tasteless. I think the meals were cooked a long time before they were 'given' (nie, zle slowo - meals are SERVED).
On the wall hung old pictures, next to (przedimek) window was a bed, 'who' (od kiedy 'lozko' ma ludzkie cechy - lozko to 'it'-ono) was uncomfortable. The room was dimly lit and stank (ale czym- perfume, beer, vodka?) When 'i' (DUZA litera) asked (przedimek) 'recepcjonist' (ortog) to change my room, she was very outraged and she told me that this is impossible, because all (przedimek) rooms are booked.
I expect you to change the rules prevailing in the hostel and that 'your's' (tutaj jest zwykle YOUR) staff 'will be' ARE more friendly. If you listened to the problems of (przedimek) guests and you 'will try' TRIED to help, they certainly 'will' WOULD be more satisfied.