The usage of the word ‘their’ in the first sentence is supposed to be referring to a location, but the word used is referring instead to the ownership of something by a person or group. The word should be spelled ‘there’. This same error occurs in the second sentence although it corrects another error seen in the first sentence – the use of the word ‘have’ instead of ‘be’ as it is used in the second sentence. Have can be used to indicate possession. Because the word follows a location, this sentence should read ‘there must be a fight’ indicating present tense.
The second sentence, other than the misuse of the word ‘their’ also contains a spelling error on the word ‘preste’. It is believed this word is being used to describe a priest as this would fall within the context of the sentence and would also be an accurate unit of measurement in the context of the extract as it would not be expected that a group of students studying holy scripture would be inclined to fight. A better word to use here would be ‘seminary’ as this is the term typically used to describe the types of schools that future priests attend.
The third sentence, although it agrees in tenses, has the tense turned inside out. Plurals should be placed on ‘fights’ and ‘arguments’ while ‘start’ should remain singular. Similarly, to make the cases agree in the fourth sentence, ‘would’ should be changed to ‘will’ to keep it in present tense.