The internet connection is very slow on this train.
con-nes-SIONE — stress on third syllable. LEN-ta — stress on first syllable. Lenta (slow, feminine).
Say this to a fellow passenger or conductor to commiserate about poor Wi-Fi, or to set expectations before lending someone a hotspot.
La connessione internet (the internet connection). È molto lenta (is very slow) — lenta agrees with connessione (feminine). Su questo treno (on this train). This is a practical observation often leading to tips about using mobile data instead.
Uso i dati del telefono invece del Wi-Fi.
I use my phone's data instead of Wi-Fi.
I dati del telefono (mobile data) — often faster than train Wi-Fi in Italy
Il Wi-Fi non funziona nelle gallerie.
The Wi-Fi doesn't work in tunnels.
Gallerie (tunnels) — signal always drops in tunnels on any Italian train
Posso usare il suo hotspot?
Can I use your hotspot?
Hotspot is used as-is in Italian — asking to tether is fairly common among travellers
The Apennine base tunnel between Florence and Bologna is Italy's longest rail tunnel at 18.5 km — the Frecciarossa passes through it in about four minutes, with no Wi-Fi or mobile signal throughout.