How to make a human corp network?

Question

Computer networks

at the moment there is a tp-link wireless router Model TL-WR940N / TL-WR941ND, two 16-port unmanaged D-link 100mb switches, three tp-link wifi repeaters, 2 video recorders with cameras, 2 wifi antennas (1km)
So, I think that you need to redo everything and do it wisely
1. change the router (I looked after the Cisco RV320-K8-RU Router)
2. separate user traffic from Wi-Fi and DVRs
3. put a backup Internet on the router, you can use a 4G modem
4. buy another switch for 24 ports or replace everything with one 48 port.
In general, what do you recommend?

Answer 1

Works? Do not touch. It does not work - you collect requirements / specifications / technical specifications for the network and make a network for these requirements.

Answer 2

Write for yourself in a notebook:
1 - what problems are there now
2 - what problems are likely in the future
3 - how each device solves these problems
Go through the list of what you want to buy, etc. and more precisely. Because right now there is not enough information.

Answer 3

I would not advise replacing several switches with one. Better half an office without internet than the whole office.
100 megabits is of course a terrible archaism, but if there are ip phones, they will still cut the speed.
as the gateway look towards kerio kontrol. maybe there will be something interesting