I saw that I need two licenses for two PCs.
Here is my question: can I buy one license and use it on my PC and smartphone? Or I need two licenses too?
It is not possible to install eM Client on your phone.
But to use it simultaneously on two computers, each installation of eM Client will require a license. If you only have one license, you will need to deactivate it on one device before activating the same license on another device.