While I am training my muscles look good, tight and strong but after I finish training it's not the same look.
I want to know if there is anything that can help me to keep the same look as I have during training?
The effect you are describing is commonly called a 'pump' and is caused by a high volume of blood being pumped into an area that is being actively worked out. The reason this occurs is to push nutrients into an area and flush waste products back out again.
As for how to maintain your pump outside of the gym, it is not possible for the above reason. This is because when an area isn't being worked out the body detects a lack of need for increased blood supply and returns to normal.
If you are looking for ways to ensure your muscles look their best, first and foremost you want to keep as low a body-fat percentage as is possible and healthy - so in the 10%-15% range for men and 15-20% in women. The less body fat you carry, the more your muscles (and the separations between them) will stand out visibly, even in an untrained relaxed fashion. Secondly, you can try induce a pump. Before you go out (to a date, bodybuilding contest, or the bank) do a few sets of high-rep, moderately low weight sets to flush blood into the area. However, this will be temporary and will impact your ability rest between regular exercise sessions.
Alternatively, there are synthetic oils that people inject into their muscles to enlarge them, however these are expensive, relatively short lasting and provide an unnatural and unhealthy look as the muscle does not deform with movement as normally happens.
When you train, your blood pump to the working out muscle and thus it looks bigger. After you train your muscle wont require that much pumping and thus the muscle bigger smaller. What I do to maximise my gym workout is that I use pre workout to enchance the blood flow and the oxygen level.
In addition, there are other tricks to use if you want to look tight for a specific day/weekend, but its difficult to maintain all the time. I agree with all the lower fat, muscle pump info already given.
In short, minimise your water intake for 2 weeks, this is hard and not to be recommended without knowing what you are doing (which is why I'm not being very specific). This on its own tightens your skin over the muscle. Then having had no creatine monohydrate for 2 months either, then ramp up your creatine through a heavy loading phase for 1 week, leading up to your target day or weekend .
The creatine will force additional water into your muscle (not skin) and give you an additional pumped look on top of everything else. Its not permanent, but can be used to good effect for a short period.