Staying on Debian 9 is a security risk since it doesn’t get any updates after it’s EOL.
I went from 9 to 12 (Bookworm) and it’s SOOOOOOOOO much better. Unless you haven’t been doing backups etc there should be no reason to stay on 9. I would advise you go to 10 and then 11 but that’s just me, because every time I’ve tried to jump that much I’ve wound up doing a fresh install. Yes my luck sucks 
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