I have just started my iTalki journey last week :) So I think my level is the same as yours 2 years ago :) I am excited and eager to learn. hopefully I'll feel the same after 1 year ? haha

It means that I am up to date. Say for example, you are watching a TV show and you have seen all the episodes and you are waiting for the next episode which will be available next week. Then you can say that "I am caught up, to the latest episode on the show". To catch up, means to be up top date or have the latest information or doing something that makes you "latest". You can even do this while running. I have to "catch up" with those guys who are running ahead of me, or I will lose the race. Hope this helps you to understand the phrase "To catch up". "Caught up" is the past tense. "I will catch up" is future.

Lighthouse

Taiwan have has a totally total of 36 lighthouses dotted around the coast.Taiwan's first lighthouse was built in Tamsui in the 17 centry, century. Many of the boats were guided by those importantly buildings in the rough ocean. Today the lighthouses has have become a beautiful landmark of tourism, but although some of them are still in use.
Every year, many people fluct flood into those iconic buildings for various reasons, like tours, to get married or to take in a great view, whatever how far from you. however far they live. 
Don't miss seeing those important buildings in your next tripe. If you visit Taiwan, your trip will not be  be complete not completely without see one of this these lighthouses.

diary ＃4. I am a negative person( I need correction from many people.)

Recently I feel that I am very boring. I have never worked in a job that is unique or interesting. I have never been to foreign countries. I have no hobbies . I can't be am not interested of in anything. Actually I'm single, so I should be able to do anything, anytime. Even though So why am I bored with myself ?

最近、自分がとてもつまらない人間だと感じます。かわった仕事や面白い仕事をしたことがないし、外国に行ったことがないし、無趣味で何にも興味がもてない。
独身だから、やろうと思えばいくらでも新しいことにチャレンジできるはずなのに、なぜこんなにもしょーもない人間なんだろう。