For Belgium and the rest of Western Europe the transit is seen from begin (ingress) till end (egress). Timing is set below - be aware this is UTC which means for the region Time=UTC+2h and these are depending of the location of the observer - changes up to a couple of minutes.
Never look at the sun with the naked eye!! Use special sun filters or use projection methods to observe the transit. Below figure shows how Mercury will move across the sun.