I heard the 29 degree of zodiac sign is very powerful? is this true?
It is right on the border of the signs, obviously, so it puts the planet in a position (unless retrograde) where they are preparing to move from one country (sign) to the next. If you have ever moved, especially to another country, you know this really changes your normal routine and you are rather preoccupied with the move and are not capable of doing much else.
The 29º degree could be powerful when the planet in that degree falls into sign harmonics that are very good for it. This would vary planet-to-planet and sign to sign.
Also the 29º degree might be powerful for other reasons – for example if that is where the cusp of the house is / where the ascendant is, or in a geometric relation to where some other planets are.