看这句英语有语病吗？

有。
前半句是一般现在时，经常或者习惯性的动作和状态。
结构：主语+ 谓语（动词原型，动词现单三）+其他
不需要was，且practice要加s
后半句坚定地相信，firm是形容词，应该改为副词firmly。in future是一般未来，不能用could，用can。
改完后应该是：He practices English language hard everyday，and he firmly believe that he can get to successful someday in future

语病很大，一是主从复合句的时态前后不搭调，没能正确呼应。二是everyday用法错误，正确的应该是时间副词短语every day，分开写。
改正:
He practices English every day, and he believes he will master the English language one day.

practising 过去进行时，要用ing形式
firm修饰believe 要用副词 firmly

有语病。修改如下：
He was practicing English language hardly everyday,and He firmly believed that He could get to success some day in future.