how to translate these sentences?

1.我认为费这么大劲不值得.
I don't think it worth the effort.
2.他似乎该为这一错误负全部责任.
He seems to be responsible for all these mistakes.
3.我想到了他可能在撒谎.
I occured to me that he might be lying.
另外,夜黑沉沉的,我们什么也看不见.
it was a such dark night that we could not see anything.(为什么这里要用could?)
因为这是描述过去的情况.could是can的过去式

1.我认为费这么大劲不值得。
I don't think it deserves so much effort.
这句用deserve比较贴切.
2.他似乎该为这一错误负全部责任。
He seems to be responsible for this mistake.
这样译简单明了,"这一错误"用this mistake就好了,没说"这些错误",因此...

1.I think it is not worth to spend so much energy on this thing.
2.He seems to take full responsibility for this error.
3.I thought that he might be lying.
could是can的过去式。was引出应用could