i've read that man can't combine workout and yoga, other words, you should do workout in certain times, when you don't do yoga, and vice versa. is it right? should i do so?
Not true, in fact the opposite is closer to truth. Doing yoga enhances workout capabilities long-term.
How you want to time exercising and yoga depends on your personal goals and personal situation, level of fitness and the type of yoga and exercise you do. So, there is no set answer for this. It's highly situational.
i've read that man can't combine workout and yoga, other words, you should do workout in certain times, when you don't do yoga, and vice versa. is it right? should i do so?
I don't know where you read this but I've often done the basic spinal series of kundalini yoga before a physical training session's warm up, and a tailored hatha yoga routine as a cool down at the end of the session.
If anything, it improves the quality and outcomes of your session.
The yoga makes the body and muscles more flexible, increases range of motion and the strength of everything along that range of motion, and opens new pathways for the circulation of energy and blood.
All of these are very helpful for athletes. It is a good idea to follow the way Stormblood said to do it.