给朋友留言是我们日常生活中的一件小事，但是用英语写留言却是一个不小的挑战。下面是一些简短的句子供大家参考：

1. 'Hey friend, just wanted to say hi and let you know I'm thinking of you!'

2. 'Hope you're doing well and having a great day!'

3. 'Just wanted to drop a quick note to say thank you for being an amazing friend!'

4. 'Miss you so much and can't wait to catch up soon!'

5. 'Sending you lots of love and positive vibes today and always!'

这些句子都很简单，但却能够传达出我们对朋友的关心和爱。当然，如果您想要表达更多的话，也可以在留言中加入一些个人化的内容，让留言更加温暖和有意义。