Good evening, please, I have a problem with my iPhone

Only you would know if there are other Apple ID's on the device, i.e. either created by yourself or if the device had a previous owner which you have denied. The only way to turn off an Activation Lock -- Turn off Activation Lock - Apple Support.

What the device is probably asking you to do is to login to it with your Apple ID & password, not to login to iCloud.com as the latter is best done from a computer browser as that is the most optimal.

As for seeing this Activation Lock, is this device you recently acquired a used device?

What do you mean by "entering the iCloud on the mobile"? Are you trying to login to iCloud.com from the iOS device?

Then login to the device with the same Apple ID & password you use to login to iCloud.com.

Are there any other Apple ID's currently on the device?

Neither I nor anyone else here on the forums can assist with gaining access to that device, sorry.