I have the problem that the page of my email provider (ionos) loads very slowly on a PC in the network. In particular, the email attachments download very slowly (a few kb / s). The problem occurs in different browsers. The PC is connected to the router via a LAN cable. Other sites load very quickly as usual (speed test at wieistmeineip resulted in a download speed of 55MB / S). I've already cleared the cache.
The problem does not occur with other PCs / laptops that are connected to the router via WLAN, so it can't be due to Ionos.
Frankly, you have to check and test such problems on site on the device.
At best, you can guess via text chat and the description. 🤷♂️