Thanks once again.
I have changed log backup frequency to every hour and
I was looking log backup size on my backup drive and it shows for each hour after changing:
8 AM 7013 KB
9 AM24897 KB
10 AM45385 KB
11 AM43220 KB
12 PM419318 KB
I have just checked - select name,log_reuse_wait_desc from sys.databases and log_reuse_wait_desc shows Log_backup and also checking to VLfs, total files around 490 and 33 files with status = 2.
Also ran, DBCC SQLPERF(LogSpace):
Log Size (MB) Log Space Used (%) Status
14198.80.17199950