Yes, it is possible, up to 128 GB. However, I don't know how many RAM slots are empty exactly. If you're interested in the information about the motherboard, it's an MSI B550-A Pro

According to our supplier reference it's a RTX3060 12 GB.

The PC has no wifi

In the specifications of the manufacturer https://www.captiva-power.de/produkte/pcs/highend-gaming-r60-406#search-begin there is no information about WLAN connectivity. I assume that no WLAN module is installed here. However, there are simple USB solutions that make such PCs WLAN-capable, such as https://www.digitec.ch/de/s1/product/tp-link-archer-t3u-ac1300-mini-usb-30-netzwerkadapter-10857405.