I am a teenager who prays the Divine Office as a basis for daily prayer. Is it appopriate for me to pray the Hours in both Latin and English (or sometimes Latin and Filipino, my mother tongue)
Yes it is licit provided approved translations are used. The abbey I’m associated with prays Lauds and Vespers in Latin Gregorian chant, but the readings and intercessions are in French. You can mix elsewhere as well such as hymns, psalms and canticles, again using approved texts.
On the other hand you can pray in Latin but use any vernacular translation as a aid to comprehension.
This is no different than a bilingual mass. I’ve often attended Ordinary Form masses where most of the mass was sung / said in English, but the Gloria, Agnus Dei, and perhaps a few other parts of the ordinary were sung in Latin.
As OraLabora pointed out, just make sure you’re using approved liturgical translations otherwise it ceases to be the liturgy of the Church and becomes a private devotion.
Nothing wrong with a private devotion, but it can never have the same merit as the Liturgy.