答:有问题.
It is worthwhile to study English well.这句话已经完整,English作为专有名词,后不需要限制性定语从句.如果补充说明,用非限制性定语从句的话,一般用逗号隔开,将for去掉,否则定语从句没有了主语:
改:It is worthwhile to study English well,which is beautiful and unique.
译:学好英语是很值得的,英语是优美的,独一无二的.
还可以改为:...,for it is beautiful and unique.