Standing vs Sitting
It is a consensus of opinion in Islam that a person has to stand in prayers.
Loading Qur'aan Verse
If the person is unable to stand, then they can sit or lie down and pray depending on their condition. You can sit on a chair or on the floor whatever is comfortable for a person.
Loading Hadeeth
Takbeer vs Recitation
It is also a consensus of opinion that recitation of the Qur'aan (in prayer) can only be in Arabic.
Loading Qur'aan Verse
The obligatory parts of a prayer literally takes less then 20 minutes a day so for the rest of 23 hours and 40 minutes a person can read the Qu'raan, ponder upon it in any language they wish.
Some Scholars have given the leeway that for those who are learning they can say the "Takbeer" i.e. Allahu-Akbar etc in their own language in the beginning.
Having said that, there is NO expectation for someone who does not know how to pray to go to fully reciting the prayer in 1 go, it will take time and its fine.
I have seen an 84 old new Muslim with Alzheimer who used to memorise Allahu-Akbar and then forget about it in 20 minutes and he went through years and did not know anything. This brother was Catholic and he had thousands of pounds worth of Christian statues which he disposed, with little savings he went for Hajj (did NOT know much) and passed away a few months later. He used to forget his Muslim name (which he picked himself) and then pick another name (and forget that too).
Another Turkish brother began to start praying in really old age and could NOT memorise but kept trying and failing.
Both have passed away and may Allah Ta'ala grant them paradise (Ameen).
It is the intention which counts, I have met Muslims who could not memorise prayers after years of trying and it is what it is but prayers are in Arabic. Majority of Reverts have no trouble after a few weeks (Alhumdolillah) but some will for one reason or another.
Loading Hadeeth
It is, what it is.