求翻译：以前，我总以为我很强，但是自从我学习直通车之后，我改变了我的想法，我在这个班中排行相当的差。我的基础要比他人略输一筹，而越难的知识我却掌握的很好。很久以前，在我学习泡泡少儿英语时，我就是一个名副其实的差生，但是自从我那留学的大哥激励我之后，我在那个班变强了，我甚至在那个班中可以排行前三。就是因为这样，我的基础不牢，而难的知识却牢牢地建在上面，如一座楼，下面是劣质水泥建造，而上方却是千斤的合金。是什么意思？

I always thought I was strong, but since I learned the train, I changed my mind, I ranked in this class difference. My basic than others slightly lose, the more difficult the knowledge I was master good. A long time ago, I learned the bubble children English, I was a truly poor students, but since t