If you click the word for each category (this is a hyperlink) you will see in the query log the queries that fell into each category.
Blocked - it is in your gravity list or local domain entries and was blocked. Never went to an upstream DNS server.
Cached - Pi-hole has the answer in memory, and that was what was sent back to the client. Also never went to an upstream DNS server.
Fritz.box - Pi-hole didn't have an answer, so the query went to the Fritz.box for resolution.
Other - kind of a fill-in category for things that aren't in the three categories above.
Pi-hole can't tell you from the queries received if a client is bypassing Pi-hole. If the client is bypassing Pi-hole, Pi-hole doesn't know it.
The network table is an overview of clients that Pi-hole identifies on the network. This can help you identify network clients that are not using Pi-hole.
I figured Pi-Hole filtering queries for IP-addresses. So any request either gets an answer or not. The configured DNS-upstream or the cache are the instances Pi-Hole itself looks for (positive) answers.
As I've just a single DNS configured (192.168.178.1) I'd expect only this to be asked. In my case there are no "others". The Pi-Hole should get an address either from DNS-upstream or from cache - but nowhere else! I suspect these "others" bypassing my Pi.
As jfb has explained, the other category serves as a pool for all requests that would not fall into one of Blocked, Cached, or configured upstreams (which is currently just the Fritz.box in your case).
If you take a look at the Status column, you'll notice that all of those entries shown have a status of OK (already forwarded), i.e. a client has re-requested resolution for a domain that Pi-hole already has forwarded upstream, but not received an answer for yet.
Again, that specific duplicate request was not forwarded upstream.
To repeat:
The other classification is nothing to worry about.
In particular, it doesn't indicate that Pi-hole is being by-passed - on the contrary: It shows requests that Pi-hole has received from your clients.