I can't speak English fluently as I am out of practice.

我不能流利地说英语，因为我已荒疏了。

《新英汉大辞典》

I can't speak English very well.

我的英语无法说得很好。

youdao

I feel stressed out because I can't speak English well.

我感到紧张是因为我的英语说得不好。

youdao

And Mr Buckles admitted: "I can't say categorically that all the guards recruited by G4S for the Olympics are able to speak fluent English".

BBC: G4S 'regret' over Olympic staffing