I have some problems with my mesh

I have these Decos

3 X55 (one is the main principal, all of them connected by ethernet)

2 X60 (one connected by ethernet and other by Wifi)

1 X50 Outdoor (connected by Wifi)

And a TP-Link TL-SG108 8 Port Gigabit Unmanaged Ethernet Network Switch to do the ethernet connection with the Decos.

I have an internet service of 350MB (download/upload), and I have almost 60 appliances in my home like Echos(Alexas), security cameras (Eufy), Smart TVs, cellphones, computers, smart light switchs, etc..

The first problem is... only I get 200-250MB either in the Decos that are connected by ethernet, but never 300 or more.

The other problem is that I am suffering for example in the Smart TVs lost connection of the internet or very slow connection then I swith the wifi connection to the main router (the one of the internet company) and then fixes, another times I can´t do the connection with the Wifi of the Decos, with the security cameras always have a lot of connection problems, the image in the app was very slow or I can´t open the camera (image), so many problems with the connection for the cameras so I decided to connect them (almost all) the the Router of the Internet supplier and the problem was solved, the cameras are working fine since then, with the Smart Light Swtichs I have like 16 and some of them lose the internet connection so is frustrating because all works with Alexa, also have problem with the cellphones sometimes the internet is slow and other times can´t do connection with the Wifi of the Decos.

The fix that I do to solve all this is to restart the Decos and then all fine again but i need to do this several times in the day, also I set the restart in the night every day but then the problem to do this is in the morning some of the appliances don´t have internet connection.

So all this is very frustrating because I spent a ot of money to buy the Decos and the ethernet cable installation to have a very nice Wifi Mesh but I can´t have it as you see.  =(

Any tips, suggestions or help can you give me to try to solve my problem?, really thank you so much in advance!