question

I am writing my experience in the past to my friend. So I am using past tense.
But if I want to express my thoughts at that time, can I use present tense?
For example,

I was very excited at that time.
How can I speak in English?
How can I .......?
How ...........................?
After thoughts on various trends, I became very frighten.

You still want to use the past tense:

I was very excited at that time. How *could* I speak English?

I was very excited at that time.

"How can I speak in English", I thought.