1.didn't be乍看起来没错,但外国人不这么用,do（did的原形）叫助动词,be是be动词,基本不同时出现在句子了. 改成wasn't比较好,个人感觉更好的是改成hasn't been
2.opportunity（机会）不知道是你拼写错误是打字笔误了,总之还要将它改成复数：opportunities
综上,基本上你的句子应该改成:He hasn't beenwasn't aware of his wasting a lot of opportunities until graduating from college.
这样基本没有致命错误了,但看着总是让人不舒服.因为像until graduating这种都是用法比较少见的.
友情奉上我的两种翻译,个人翻译,不作权威,纯粹交流：
1.Not until he graduated from the university was he aware that he had wasted many opportunities.
2. He wasn't aware that he had wasted a lot of opportunities until he graduated from college.