I spoke to the weights trainer at my gym this morning and he said 30g is fine. I told him I have been having around 80-120g and he said all what will happen is the protein your body doesn't need will come out in your urine and it will smell like amonia
No, 30g is decidedly not fine, unless you want to lose a lot of lean mass along with your body fat. Even the most conservative recommendations call for 0.8g of protein per kg, which in your case would be 180g per day.
Since protein needs increase while in a calorie deficit (because some of the protein will be oxidized for energy rather than tissue repair, maintenance, and growth), recommendations during a weight loss phase are even higher. And if you're performing regular exercise, and weight training in particular, the recommendations for achieving positive nitrogen balance range as high as 1.25g per pound of weight.
See, for starters:http://ajcn.nutrition.org/content/88/5/1322.short
Dietary protein requirements of younger and older adults
Contemporary Issues in Protein Requirements and Consumption for Resistance Trained Athletes
Tracer techniques have been recently employed and generally support the protein requirements obtained through nitrogen balance studies [13,24]. In fact Tarnopolsky et al.  found that protein synthesis increased from low (0.8 g/kg) to moderate (1.4 g/kg) intakes. While there was an 8.6% increase from moderate to high (2.4) protein intakes, these results did not reach significance. The authors suggested that this non significant trend appears to support the suggestion that the real protein requirements of athletes were closer to the 1.8 grams of protein per kg of bodyweight daily.
I don't say this lightly, but if this trainer told you that 30g of protein per day is sufficient, you should never
seek dietary advice from him again.