Original: 우리 엄머니한테서 선물을 받았어요

Again, ALL the spacing is correct!!!!!!! I'm so proud of you! There are just two SMALL corrections that I would make to this sentence to make it better~ So firstly, whille     어머니 is the proper way to call your mom, when referring to your own mom and telling someone else, you would use 엄마 (informal) to make it sound more natural!  Secondly, adding the 서 is grammatically correct but if you want it to sound a little more native you can take out the 서 :) These are all just suggestions but you did a GREAT JOB and the corrections are just there to make you sound more native~

You guessed it! You have to change the particle because the character before the particle doesn't have a 받침 (the part on the bottom) so it would be 는 instead of 은! If you were talking about 선물 for example because there is a ㄹ at the bottom of the last character you would say 선물은! Hope that makes sense!!!!!