There arewas a lot of foods but most of them awere expensive.

This should be in past tense since it already happened.

By the way, today’s performance iwas stand-up comedy.

It iwas the first time I watched a live performance.

Congratulations!

It’ was hilarious.

The comedians had a good interaction with viewersthe audience.

In the evening, we went to an exhibit of lanterns that iwas being held in the city where I haveused to lived.

It iwas held around the lake and there awere many food stands.

Although the food iwas delicious, it iwasn’t like the lanterns exhibit that I saw before.

It’sThere were only a few lanterns and they awere all made out of balloons, not like the traditional ones made of iron wires.

I thought it was thea fly in the ointment.

SThe stock market was open after ten days of being closed.

Many of my friends invest some money in the stock market.

It's been so long that I finallybut I waited until the situation I anticipated.

I’m learning from the podcasts and books.

Today I went to the New Year market with my high school friend.

more idiomatic (aka sounds better): with my friend from high school

There are a lot of foods but most of them are expensive.

There was a lot of (different) foods but most of them were expensive.

Therefore, we only bought four kinds of snacks.

Therefore is very formal-- maybe use 'so'

By the way, today’s performance is stand-up comedy.

past tense-- 'was stand-up'

The comedians had a good interaction with viewers.

The comedians had good interactions with the viewers

In the evening, we went to an exhibit of lanterns that is being held in the city where I have lived.

-> lantern exhibition + that WAS

I thought it was the fly in the ointment.

'a fly'

Stock market was open after ten days of close.

The stock market opened after ten days of being closed

It's been so long that I finally waited until the situation I anticipated.

It's been so long that I have been waiting for this situation (you don't really need to say 'situation' here, feels stilted) which I have been anticipating.

The only thing I consider is whether this company gains profits or not.

'this' change to 'the'

I’m learning from the podcasts and books.

delete 'the'

There are ais lot of foods but most of them are expensive.

Or "There are lots of..."

Therefore, we only bought four different kinds of snacks.

Instead of kinds you could say "types"

By the way, today’s performance iwas stand-up comedy.

It iwas the first time I watched a live performance.

It’ was hilarious.

You will have already watched the performance by the time you write this so you need past tense.

The comedians had a good interaction with viewersinteracted well with the audience.

In the evening, we went to an exhibit of lanterns that is being held in the city where I have lived.

It’sThere were only a few lanterns and theythat are all made of balloons, not like the traditional ones made of iron wires.

SThe stock market was open after ten days of it being closed.

Many of my friends have invest somed money in the stock market.

It's been so long that I finally waited until the situation I anticipated arrived.

I’m learning from the podcasts and books.