It is 19.5 meters long and 8 meters wide. Is the middle section a square, 8x8 meters? The other 2 sections appear to be about 11 meters. Is there a door on the opposite side to the door shown here?
I think I have good news for you, Chimera. The following is a very interesting web site run by "Wągrowieckie Stowarzyszenie Szlaku Cysterskiego", Wągrowiec's Cistersian Trail Association, handling anything related to Cystersians at the vicinity of Wągrowiec, including Tarnowo Pałuckie. Here is their page about the church in question: cystersi.wagrowiec.pl/folder4.htm
If you read Polish than you are on your own - you will find it a treasure trove of professional information. Otherwise I will gladly give you a hand in translation of details of your interest.
The old church, built before 1263, stood on a stone foundation and had dimensions 19.5 m by 8m. It was actually made of two parts: a nave and a narrower rectangular presbytery at the east side. According to current findings that church has functioned until last quarter of 14th c. The new church was set on its place, whose main block has been preserved to this day.
The web page includes the plan of St. Nikolaus (Św. Mikołaj) Church in Tarnowo Pałuckie:
1 The main altar
2 Side altar of St.. Nicholas
3 Side altar of St.. Margaret
4 Rainbow arc beam;
5 Musical choir (gallery)
9 Wall with scenes from the life of St. Margaret
10 Wall with scenes from the life of St. Nicholas;
2 IPW monogram of the alleged author of polychromy
13 Old brick porch (now removed and replaced by a wooden one).
As is apparent from dendrochronological studies, the vestry and probably the nave were built in the last quarter of the fourteenth century. The oldest wood used in its construction has been cut in the autumn / winter 1373/1374. Various building and restoration works were conducted on several occasions. For example, in 1628-1629 the roof truss was replaced and about in 1639-1640 the west tower added (the dendrochronological findings are supported by the date 1639 carved on the beam above the entrance from the tower to the church). The church and the tower were restored several times, most recently in the nineteenth century.