Sounds like you came from Android 5.1 and now updated to Android 6, so here’s some reading material for a start …
https://support.fairphone.com/hc/en-us/articles/115001671246
About the feature you mentioned … Fairphone dropped it, the community salvages what’s possible …
If you miss silent mode …
And how to connect your phone to a PC now (the following post doesn’t apply to Macs only) …