Three months in the first year - שלשה חדשים בראשונה
There is a dispute between רש"י and תוספות whether during the two, three (one) month, cycles the מחזיק is required to both plant and harvest the crops (רש"י); or whether it is sufficient that he either harvest or plant the crops (תוספות).
He harvested the produce of his grapevine - כנס את תבואתו
The בציר of wine is in תשרי with the olive oil season sometime thereafter. The figs are either harvested after the oil season, or are harvested during סיון, but not taken into the house until after the oil season. According to the ר"ח, the figs are taken into the house (immediately) after they are finished being dried in אב.
If you will argue; just as a שור המועד, until the fourth goring, etc. - אי מה שור המועד עד נגיחה רביעית כולי
Originally, רש"י maintained that there is a dispute between אביי ורבא whether a שור המועד pays a נזק שלום on the third נגיחה, or on the fourth נגיחה. However from our גמרא it is evident that all agree that a שור המועד pays a נזק שלם only at the fourth נגיחה. Their dispute may be whether the fourth נגיחה can be on the same day as the third נגיחה, or it must be the next day.
Until the fourth goring he is not obligated - עד נגיחה רביעית לא מיחייב
There two ways of understanding how we derive חזקת ג' שנים from שור המועד; either a. A pattern of behavior is established when something is repeated three times, or b. The rules and laws change when something is repeated three times. Our מקשן assumes the second view.