I have a problem of opening of raspbian. I installed the raspbian and then after installing a dialogue box showed that installation is successful, after i press ok the monitor shows no signal and then i unplug and plug the rpi4 but after doing that it shows rainbow Screen and if i do nothing it shows no signal and if i press shift there is recovery and just installs it again. How to solve this?
Despite the Comments the rainbow screen is unlikely to have anything to do with power supply - it is indicative of missing/faulty boot files.
Again contrary to comments the Pi4 does NOT REQUIRE a 2A (or 3A - as recommended) power supply - it will boot and run on a good 1A supply, although a quality (official) supply is recommended.
See Pi4 Boot Problems Sticky which will help you diagnose your actual problem.
NOTE the rainbow screen is not a meaningful indicator on the Pi4.
You are recommended to download Raspbian and follow the installation guide. https://www.raspberrypi.org/downloads/raspbian/