So, after 2 years of abstinence from gym, I finally decided to hit the weights again. Now, I've heard all kinds of bad things about "Bro Split." But my trainer (really strong and in shape guy) recommended me to do a bro split workout where I train one muscle group each day, really intensely. When I pointed out that bro split get a very bad rep, he said not to worry about the bad rep and I should be seeing results in a month or two with this workout if I stick to it and eat proper diet. Now, I fall in the category of Ectomorphs or Hard Gainers. So, I'm worried that If I start with a wrong approach and see no results later, I might give up working out altogether. Any advice from an Ectomorph who successfully put on healthy weight?

My current workout routine goes like this:

Monday-Chest Tuesday-Back Wednesday-Shoulders Thursday-Arms Friday-Legs Saturday-Abs Sunday-Rest

And my current physique: Really underweight 5'11" guy in mid 20s.