MacBook – Internet dosn’t work when connecting hdmi / usb hub

I've had this issue on my Macbook as well and found that if you go into terminal and clear the cache it loads the pages again.

Type dscacheutil -flushcache

I would go for USB-C to DisplayPort directly. That would be one relatively inexpensive ($20 to $40 US prices) cable to do the job. Since your display won't charge the MacBook and do video over a single USB-C cable and you have several ports (display side and Mac side) - a dedicated cable would be my choice.

I like the USB-C to HDMI adapter you mentioned for my MacBook since there is only one port and charging plus USB is needed, but on the MacBook Pro you have several ports and can use one per display without too much hassle. It will work for you, though - just not my first choice.

Apple even recommends against using the adapter you mention for bridging between a Mini DisplayPort device and thunderbolt 3. - https://support.apple.com/en-us/HT204154

Note that although it uses a Mini DisplayPort connector, the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter doesn't support connections to Mini DisplayPort displays.

If you only want two external displays, both 13 inch models of MacBook Pro are suitable. You'll need the 15 inch models to support 4 displays. That might be a non-issue if you only have one Dell display to connect.