I like that you were able to research the context of the attack and use your findings to disprove the original claim, however I wish that you had written out more of your process because you have presented some conflicting information.
You say that NATO launched a 78-day bombing campaign, however, in the US Holocaust Memorial Museum article that you provided, it actually states that it was only a three-week bombing campaign in August 1995, and the war concluded with a peace agreement that was signed in December 1995. There are more than 78 days between the end of August and the beginning of December, so based on your answer alone I cannot tell what event(s) you are counting as the last day of the campaign.
To give you the benefit of the doubt, I looked into an article I found from Brittanica about the Dayton Accords (
https://www.britannica.com/event/Dayton-Accords) that states they were signed on November 21, 1995. This would indicate a number closer to 78, especially if you counted any dates leading up to the signing. My point being, where did you get the number 78 days? What events are you including in this number, or if you got it from somewhere else, what are they including?
Additionally, the statements you made by means of fact checking a claim could also do with some fact checking themselves, such as when you said NATO's attack "slow[ed] the effect of the oppression" of Albanians in Kosovo. What does this mean tangibly and statistically? The purpose of the fact check is to provide more evidence, so introducing new claims without explaining the evidence is counterproductive.
I think that you were on the right track with your fact check, but could have used more time checking multiple sources and explaining your thoughts more clearly.