Unable to acquire the lock.

Hello, well, I haven't been using Ubuntu for long, but my problem is that when I'm in the software center and I click on install the software, it gives me "unable to obtain the lock" after a few seconds. So I really need someone to help me solve this. And the problem is that I didn't have any other package managers open. Best regards. Thank you in advance. I'm waiting for a response as soon as possible. Thanks.

Configuration: Linux / Firefox 73.0