I have a public repository on GitHub with project and source code under GPLv3. Can I freely drop repository and close project if I don't want to develop it. And after some years maybe I want publish it again. Can I freely create new repository and publish source code again under GPLv3?
If the code is entirely yours, your choice to license your own work under the GPL does not limit your own rights in how you may distribute/modify your own code . By releasing under the GPL, you have given others certain rights to distribute and modify your work, but you have not lessened your own rights. You may cease or resume distribution of your work whenever you please (but cannot demand other GPL recipients do the same).
If you rely on someone else's GPL'd code in your project, then you are required to obey that other author's GPL requirements. However, the GPL largely only places requirements whenever you do perform distribution. You may choose to cease redistribution at any time and relieve yourself of GPL requirements at any time.
The one narrow except to this is if you have distributed someone else's GPL'd binary code with a written offer for source, which must be honored for three years. (This is not a typical distribution case.)