Help with Japanese language?

Question:

1. How would you say "I tell you" in Japanese?
For example: "There is a cat in the house I tell you"

2. Is this sentence correct for "The bookstore was not inside of this hotel"?
Hon ya wa kono hoteru no naka ni arimasen.

3. How do you say "often" or "not often"?
Example: I do not often eat vegetables.
4. Is this sentence correct for "When I was a child I wrote letters?

Kodomo no toki de tegami o kakimashita.

Thank you very much!

Answer:

1. Does that mean, "There is a cat in the house as I told you (or, as I mentioned)"?
if so, "(itsuka) hanashita youni, sono ie ni neko ga imasu."
"itsuka ohanashi-shimashita ga, -- ditto --" (written)

2. It's past tense, so; "Hon ya wa kono hoteru no naka ni arimasen DESHITA"
"hon-ya wa kono hoteru no naka niwa nakatta (desu)" is OK, too. (sounds more natural)

3. I do not often eat vegetables. --> should be "I don't eat vegetables so oftern."
"yasai wa sorehodo tabemasen." "amari tabemasen" is OK, too.
--> "amari .... -masen" can mean both "not ..... so much/many" and "not ..... so oftern"
we also say "shocchuu tabemasen" (colloquial) "hinpan niwa tabemasen" (written) for "not often"

4. I would say "kodomo no koro wa, tegami o kaite imashita" (I used to write......)
"kodomo no koro wa, yoku tegami o kaite ita mono desu" (written)