I think it may depend on the church but I think typically there is a peal before the commencement of high mass on Sunday which starts some minutes before mass and ends when the mass begins . There is a shorter peal during consecration .
Then in Catholic Tradition there are three everyday peals, which may use different combinations of bells if they have different bells . I think the morning one is at six or seven depending whether it’s summer or winter and the evening one at seven or eight . These typically announced the start and end of working days in the old times . Precise times can vary with the location and region .
There is also a midday one at noon which is more regional and no longer done in many places . Officially it marks the death of Christ on the cross and some religious people stop whatever it is they are doing and say a brief prayer . In parts of Eastern Europe and the Balkan countries it is in popular tradition understood to commemorate the defeat of Sultan Mehmet by John Hunyadi at the siege of Belgrade in 1456. Although I understand this is not an official church position .
The tolling of a single bell without any others and outside of the regular tunes sometimes indicates a funeral .
The bells used to serve a couple of purposes, to tell the time, indicate that a particular service is about to start and in the Catholic Church and so other Christian churches to call people to prayer at 06:00, 12:00 and 18:00 (The Angelus).
In olden times the people relied on the bells to tell the time and although there is no need for it now most Swiss communities keep it up, some also ringing on the half as well.
The bells are normally rung before church services and there are different sequences to indicate the type of service - an ordinary service, a wedding, a funeral and in extremely rarely occasions a high mass (these services stopped in the late 1960s and now requires special permission before it can be conducted). If you visit a church at this time then, yes you will find a prayer session in progress.
Catholic Church bells ring at 6:00, 12:00 and 18:00 to remind the people to pray the Angelus. In theory you should observe Catholics pause for say five minutes to do so, but I have not heard anyone saying the Angelus for at least 20 years! If you visit a church at that time you are not likely to see any activity.