1.首先没有I'm in a good shape这种说法，然后I'm in good shape其实说的就是healthy和immunity.所以这里你是不是想说I 'm in a good figure.

2.Running Man 咦改过了哈下面的

3.电视节目的缺点并不是disadvantages.可以说ALthough a lot of people find it XXXX。a lot 就是不少的感觉 而many就有点很多，用在这里这里读起来有点我就非要喜欢这样的感觉

4.which will be highly appreciated!似乎有点多余

感谢各位，这是修改后的，请各位看一下是否可以：

Dear Linda,

How glad I am to hear from you! Everything is excellent! How are you lately?

The weight remains,while the height has changed a lot,which translates that I look a bit thinner and I'm in a good shape now!What's more, I often exercise to keep healthy and improve my immunity. There is no denying that keeping healthy is extremely significant and necessary for human beings.

Speaking of my favorite TV shows, it's Running Man. Although many people think it has a great number of disadvantages, I do enjoy watching it!Not only can I learn quite a few jokes from Running Man, but I can spend my spare time with delight by watching it!

Anyway, I miss you as well! How about getting together one day?

Looking forward to your swift reply,which will be highly appreciated!

Yours sincerely,

Liu Lan

1.I'm much taller than before, yet the weight did not change a lot.可以改为 The weight remains，while the height has changed a lot，which translates that  I look a bit thinner and I'm in a good shape now!

while表列两个情况对比，which translates可以理解为which means，这里使用更正式。

2.I enjoy watching it!改为I do enjoy watching it!加深语气，更符合语境。

3.我也觉得应该删去 it is likely that。

初二的写作相当不错了。我只改动二处：

1 I'm much taller than before, yet the weight did not change a lot. 后面你提及所以你看上去瘦了，这里你强调的是长高了，虽然体重没有变多少。体重没变应该改为让步从句，突出长高让你显瘦这个关系。所以yet 改为 though，同时than before改为now。

I'm much taller now, though my weight hasn't changed a lot.

2 It is likely that not only can I learn ... 删去 it is likely that，这个主句没有多少实际意义，与that从句的can意义重复。直接说 Not only can I learn... 。