MicroSD speed jumped from 75 to 40

[Android Central Question]

Brand new memory card Samsung 256GB, first time i saved there data, speed was 75 MB/s (about 60GB).
Today i deleted everything and saved back 60GB data, and speed was 40MB/s.
Then formatted the card, but still speed only 40MB/s
The read speed is also down at 40MB/s