Tips for weight loss?

I’m 5’6.5-5’7 and 195 lbs. I’m trying to lose weight to at least 178 lbs so far I’ve lost 3 lbs. Everyone says I look average but I used to look kinda slim when I weighed 170-175. My gf is 5’3 and 190 lbs she used to be 165 170 lbs. We can’t afford a gym membership and she wants to lose 25 lbs. My problem is snacking throughout the night cause I’m a night owl and I want to lose 20 lbs before my 21st birthday in June