4 sentences for correction of mistakes

"On the one hand, he is very accomplished in all the subjects he takes in the school compared to the rest of his class, but on the other hand, when it comes to usual things that require manual dexterity, he fails miserably."

"We were promised to go on unforgettable vacation with our school, however, all of a sudden, our headmaster had an abrupt change of heart and though most of teachers were in favour of such an inviting prospect of being somewhere else than in the dull school grounds, the excursion was unconditionally cancelled."

"I insist that you go with me for a drink to celebrate our roaring success in the school-leaving exams."

"It wasn't until the evening that I reflected on the implications of a decision that still lay ahead of me."

Thanks in advance!