Hello. I'm going to correct your text, and I will try to explain your grammar mistakes in your mother tongue in order to you understand the explanation. I'm studiying English now and I,m not very good writing in English. so, I apologize because I'm  likely to make grammar mistakes, but I think that this is a good way to improve our language skills toghether.

Saludos desde Japón

Underlined colour meaning:

        -Green: The grammar structure It's fine, but this expression in colloquial  Spanish sounds a little strange.

        -Yellow: Grammar mistake.

-Grammar advices:

1."Hola!" --> In Spanish language we use two different symbols for the exclamation mark. The first ( ¡ ) goes at the beginning of the exclamation sentence, the second ( ! ) goes  at the end of the exclamation sentence. In this case, the correct form to write the exclamation phrase would be:  (¡Hola!)

2. "Yo soy de Canadá"--> The structure is correct but in Spanish language you needn't write the Personal Pronoun at the beginning of this sentence. You can leave it out if you want, because It sounds better and more natural. e.g. (Soy de Canadá)

3. --- ciclismo --> In Spanish we usually write a definite article before the noum (El, la, los las) which depends on the genre of the noum. e.g. (el ciclismo)

-Or you can use the verb  "hacer" in infinitive form before the noum . e.g (hacer ciclismo) I think this form to write the phrase is better than the first who I explained you. But you can use both if you want.

4. "Viendo" --> In this case, you have made a conjugation mistake. The correct way to conjugate the verb in this particular case is using the spanish infinitive. e.g. (ver la televisión)

5. "He estudiado a español"--> You musn't write any preposition here,  Beacuse you needn't. The correct form to write this (He estudiado español)

6. "durante uno semana" --> Numbers in spannish have a genre which depends on the noum, in this phrase "semana" it is feminine, so you should write: (durante una semana)

7. "de inglés" --> In spanish there is a grammar contraction for that structure (de+el =del). e.g (del inglés)

Saludos desde Japón

Saludos desde Japón