Two words are easily confused as they are both a bit alien to English speakers (and are actually weird anyway):
Tha /ha/ 'am, is, are'
Thu /u/ 'you (singular)'
There is no obvious reason for either to be lenited (Irish tá tú), and no obvious reason for the th in thu to be silent.
This is accepted now. It wasn't included initially as we are all Scottish English speakers and this construction is pretty alien to us. I thought it was ungrammatical but apparently it is common in many places. There are 12k + sentences in the course (each with multiple variations) and we are a very small team of volunteers. It will take us a while to get them all. :)
The strict translation of tha bòtannan is 'boots are'. It is the last word that says who has them and if they are wearing them or just 'having' them.
agam 'at me' I have them
agad 'at you' you have them
orm 'on me' I am actually wearing them
ort 'on you' you are actually wearing then
And of course there are words for other people as well. The details are at https://duome.eu/tips/en/gd#Clothes