there are a few diffrent answers depending on how you start your question in welsh...
question beginning with 'Ydw..?' , the answer will be 'wyt' : Do I have to send her a thank you letter - (in welsh : Ydw i gorfod danfod cerdyn diolch?)
question beginning with 'Oes..?' , the answer will be also be 'oes' : Do I have to send her a thank you letter - (In welsh : Oes rhaid i fi ddanfon cerdyn diolch?)
"You are Welsh" = Rwyt ti'n Gymreig
'Our Friends' in Welsh is 'Ffrindiau Ni' :)
To say "your house" in Welsh, you would say "eich tŷ".
Cymraeg
No in Welsh is dim.
"y diwedd" is how you say it in Welsh language.
In Welsh, you would say "Rwy'n cytuno" to say "I agree."
Draig Gymreig
You can say "it's nice" in Welsh as "mae'n braf."
Yes in Welsh is "ie" and no is "na."
Great > [Welsh] mawr
"Egg" in Welsh is "wy".