Awesome question, @Viss! 
And hooray for all the bilinguals/polyglots in the forum! 
It is so much fun hearing about everyone’s experiences using and jumping between languages in their practice 
I know there was a similar thread a while back, so if anyone would like some additional ideas about multilingualism in the Craft, I’ll add the link here:
→ Does it matter what language I cast spells in?
Others may have differing thoughts on this (and perhaps deity bonds may affect how you communicate, if you are working with a deity), but I think it is absolutely fine to jump between languages within a spell so long as you know what you are saying and the words carry meaning to you- especially if the spell or ritual is your own, or you have customized the spellwork to best suit your needs 
After all, some words just feel better in different languages, and some words or feelings you want to call upon in a spell may not even exist in other languages!
I know there are some folks who are against customizing or altering pre-written spells, but I’m in the school of thought that thinks customization is the best way to make a spell suit your exact needs. I believe that, unless the spell specifically says not to, to do what feels right and what carries the most power to you- mix languages, substitute meaningful words to you, etc! Make your spellwork your own 
Great question, Viss- thanks for asking it!