楼上翻译机器满天飞啊!
保证准确：
In one word / All in all / In a word / Altogether,I think (that) knowledge is power.So I strongly advise/recommend/suggest (that) Dennis (should) focus/concentrate/fix/center his energy and time on senior high school work nowadays / now / at present / at the moment.The reason is that it's the knowledge he is studying/learning to obtain/acquire/get and the university degree he will probably receive that are the basis on/upon which he will stay/remain unbeaten in this/the competitive society.
注：/ 表示可以任意选用其一；（ ）表示可以省略不用.