I am a Breton ultranationalist who wanted to know how to say Sussy baka Amogus without going through foreign (especially the one of my Neighbours) language

SUSSY

In Breton, suspicious can be said "disfiz" or "diskred", we will go for diskred as it's the most precise. However the word "sussy" come with the diminutive "-y" and the shortening of the word Suspicious into Sus. So i'll go with the shortening "diskr-" with the diminutive "-ig" it should be something along the line of "diskrig"

BAKA

Coming from the Japanese "馬鹿" from Sanskrit "मोह" (moha) the word mean "stupid", "idiot" or "fool". Breton can be pretty funny when it comes to sluring so the use of simple words like "Baka" is pretty uncommon. There is the French loanwords "diot" and "sot" but to get a purer breton word we should look at "droch" or "istrogell" and i'll go for "istrogell" since it comes to be the most used one from what i've seen

AMOGUS

There is two ways to treat the words Amogus

1. Amogus can be treated as a compounded preposition, that's actually fairly common among Celtic languages including Breton. However the preposition "among" doesn't really have an equivalent in Breton other than e-touez, meaning that we will conjuguate it with pronouns to make the words hon touez that I will shorten in Hontouez to make it into one words, such as how Amogus is a shorter way to say "Among" and "us"
2. Amogus can be treated as a Latin word we can either imagine an evolution into French Amongousse that would leat to a Breton Amoñgouzh or to get a purer form we can directly take it from Latin an taking how the word "Magister" became "Mestr" we can assume the word Amongus could become something like "Amañgs"

HONTOUEZ ISTROGELL DISKRIG

/ɔ̃ntuɛ(z) istʀoɡɛl diskʀik/

AMAÑGS ISTROGELL DISKRIG

/ãmãks istʀoɡɛl diskʀik/