I'm having a great time in Shanghai.
我在上海的玩的很愉快。

have a good/great/wonderful time (in)
(在...)过的很愉快
I wish you have a great time during your summer holiday in Hawaii.
祝你在夏威夷度过一个愉快的暑假。
They are all very kind and I had a great time last night.
他们都非常友好，昨晚我玩的很开心。

A:Hey,Michelle,this is my friend James.He's visiting Shanghai from New York.
米歇尔，这是我的朋友，詹姆斯，他从纽约来上海找我。
B:Hi James.Nice to meet you.So,uh,are you visiting for business or pleasure?
你好，詹姆斯。很高兴见到你。那你来这儿是工作还是游玩？
A:Well,actually a little of both.I'm meeting some business contacts but I'm also taking some Mandarin classes.
恩，实际上两个目的都有。我来这儿处理一些生意上的事情。同时我还报了普通话班。
B:That's cool.How's it going?
真棒，现在进行的怎么样？
A:Well,I'm finding the classes pretty tough actually,but I'm having a great time in Shanghai.It's really an amazing city.
事实上我发现，学习的内容比较难。但是我在上海的玩的很愉快。上海真的是个了不起的城市。
B:It sure it.Are you staying for long?
当然。你要在这儿待很久吗？
A:Only two weeks unfortunately.I wish I could stay longer but.
有点遗憾的说，只有两个星期。我多希望可以待的久一点。
B:Well,listen,if you need someone to show you the sights then just call me.I'm having a little get-together at my new apartment next week.So you can drop by then if you have time then.
如果你想游玩需要有人给你当导游 ，就打电话给我。下周在我新的公寓有个小聚会。如果那个时候你有时间，可以过来玩玩。
A:That sounds great.I'd love to.Let me take down your number,Michelle.
听起来不错，我想我会去的。米歇尔，能告诉我你的手机号码吗？