Failed logins (German: fehlgeschlagene Loginversuche)

Dear Community,
We are permanently receiving mails from WordPress (meanwhile more than 100!) with the (German) subject ?Zu viele fehlgeschlagene Loginversuche‘ which means that somebody has tried to get into our account with an invalid combination of user id/password. Example (IP and last user replaced by xxx):
———
6 fehlgeschlagene Loginversuche (2 Aussperrung(en)) von IP: xxx.xxx.xxx.xxx
Last user attempted: xxx
Die IP wurde für 24 Stunden geblockt
———-
The locations of these IP’s are: Belarus (Wei?russland), Brazil, Canada, China, France, Greece, Ireland, Poland, Russia, Ukraine, United Kingdom and USA

We have analyzed these mails and found out, that mostly all of the user id’s, the hacker(s) have used, are either real user names of our account or nick names of these users. That means, the hacker(s) must have access to our account to get the current user id’s and nick names.

Our questions:
1. Does WordPress provide a log file containing the logins, which have been successful? We do need to know if any login from an unknown IP has been successful.

2. The last sentence of these mails (?Die IP wurde für 24 Stunden geblockt‘) means that the hacker’s IP has been locked for 24 hours. But: We have received several mails at the same day containing the same IP, example: 13.08.2018, 05:55 / 13.08.2018, 09:02 / 13.08.2018, 13:28. What does it mean: The IP has been locked for 24 hours?

3. What does ?2 Aussperrungen‘ (2 lockouts?) mean in this context?

Any help is highly appreciated.

Thanks in advance,
Lothar

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