Focusing on one coin may not necessarily increase the chances of making profits but it decreases the potential loss of the capital, and yes it will help them to understand mand master the price tracking and get better predictions but making consistent profits either with one coin or many coin isn't a guarantee, we need a bit of luck too with trading to keep making money.
If you focus on a single coin, then yes, you’ll be able to study it better and understand its movements. You’ll probably start researching the project, following its news, updates, and so on. This will likely help you achieve better results with that specific coin. However, if you go too deep into just one project, you might miss out on other, more promising coins that could earn you even more. That’s why I wouldn’t recommend focusing on just one coin. You should have a few projects, maybe 3 or 5, depending on how many you can manage effectively at the same time. Over time, you’ll figure out which ones are better and more promising in terms of profit.