Les activités que j'aimais quand j'étais un enfant sont(être?) dessiner et j'aimais jouer avec des jouets et le barbie avec ma soeur qui est plus âgée que moi.

what verb do I use for:
The activities that I liked to do "was"

thanks in advance

how do you write "i brushed her (barbie's) hair, and always changed her clothes"

Je s'est? brossé les(ses) cheveux et je changais ses vêtements toujours

you can't use "s'est brosse" if you brush someone else's hair.

You would rather say "je lui brossais les cheveux"

"toujours" is always placed after the verb " je lui changeais toujours ses vetements"

As you noticed i always put "lui" before the verb which must be added when you do something to someone

"the activities that i liked to do was"

Les activites que j'aimais faire quand j'etais enfant etaient ( you have to use the past tense; sont is the present tense)...

In french, barbie is feminine as it is a doll (une poupee), la barbie (FYI -in french it is more correct to say "jouer a la barbie")

Sorry of my explanation is confusing, as my english needs to be improved (i am french)

hope this helps anyway

Your first question is NOT

was because the word "activities" is plural.
Les activités que ........étaient..... Also check "le barbie!"

Celia's help is excellent, except for the accents!.....¡à, vêtements, j'étais, poupée, etc.

Because you had difficulty with je me suis brossé...let me explain reflexive verbs. Let me explain about the agreement of the past participle.
Past participles of reflexive verbs agree in gender and number with the preceding direct object (if there is one.)
Ils se sont arrêtés court. = The stopped (themselves) short.
Où sont les cravates qu'il s'est achetées? = Where are the ties that he bought for himself? (cravates is the direct-object but it precedes the past participle)
Elle s'est brossée. = She brushed (herself)
BUT: with the verb "parler" there is no agreement because it takes the indirect-object, as in: nous nous sommes parlé. = we talked to each other.
Elle s'est brossé les cheveux. = She brushed her hair. *hair/les cheveux is now the direct-object and follows the past participle; you might rationalize it such as "she brushed her hair-that-belonged-to-herself"
Nous nous serions écrit. = We would have written to each other. (this is called reciprocal = one to the other)
Ils ne se sont pas rappelé la rue. = They didn't remember the street. "la rue/the street become the following direct-object and this is a negative sentence so you can see where the reflexive pronoun goes.

Also: past participles used as adjectives agree with the noun they modify:
Les bijoux étaient cachés. = The jewels were hidden.
Je dis que le latin n'est pas une langue morte. = I say Latin is not a dead language.

RECAP/SUMMARY
1. Past participles conjugated with "avoir" agree in gender and number with the preceding direct object, if there is one.
2. Past participles conjugated with "être" agree in gender and number with the subject. (That includes all Reflexive Verbs)
3. Past participles of reflexive verbs agree in gender and number with the preceding direct object, if there is one.
4. Past participles used as adjectives agree with the noun(s) they modify

Sra (aka Mme).

P.S. Now let's explain about the placement of adverbs.

POSITION OF ADVERBS:

1. An adverb modifying a verb in a simple tense is usually placed directly after that verb.
Il prononce distinctement ses paroles. = He pronounces his words distinctly.

2. In compound tenses, the position of the adverb varies. Most adverbs, specially long ones and adverbs of time and place, generally follow the past participle. A few common ones, such as bien, mal, souvent, toujours, déjà, and encore, as well as the adverbs of quantity, usually precede the past participle.
L:e médecin est venu immédiatement hier. - The doctor came immediately yesterday.
Nous avions beaucoup dormi ce jour-là. = We had slept a great deal that day.

ALSO: Celia example of You would rather say "je lui brossais les cheveux" is no longer a Reflexive Verb. What it is is a "Service/Disservice Verb" in that you are not doing the action on yourself BUT on someone else. Therefore "lui" indicates that.

Sra (aka Mme)

Feel free to ask any other question you may havae!

thank you so much on the lesson, I was so confused on how to write about brushing someone else's hair.

so the adverb would go
je changais toujours ses vêtements ? =)