Slow SMB write speed

When I connect to my samba share using Nemo I get around 22 MB/s using ethernet and around 2 MB/s using Wi-Fi. When I connect using "mount -t cifs -o user=*** //...." I get around 30 MB/s read using ethernet (that is the speed it should have) and then for some reason 100 MB/s write (that should not be possible since the drive I'm writing to is connected via USB 2.0), when using Wi-Fi I get around 10 MB/s reads (that is normal since I'm using 150 Mbps Wi-Fi access point) and when I try to write over Wi-Fi at first I get like 300 MB/s, it gets to around 50% and it drops to 500 KB/s. Can I do something to use the theoretical maximum (30 MB/s over ethernet and 10 MB/s over Wi-Fi) without performance drops when it gets to a certain point?

Having the strange write speeds is likely some caching happening.
But the speeds are apparently about correct