It have just started on Challenge 12 but have two questions, if any one can explain a simply version of why they are used the way they are in Challenge 11, please?
Firstly, on looking up the translation of mae, I note it means = there is. However, is there a reason why this is used at the start of a sentence ie: yr dyn ifanc or Mae’r dyn isio…
Secondly, gofyn wrthort ti. Why is it split when you add a word - (something) for example. gofyn rhywbeth wrthort ti.
Different languages have a different normal word order. Latin and German, for example, put the verb at the end of the sentence. English goes subject -verb-object, as the young man (subject) sees (verb) the dog (object). Welsh is one of the languages that goes verb-subject-object, literally: sees the young man the dog. Mae, is a verb so it normally goes at the start of the sentence. The man is young in Welsh is Mae’r dyn yn ifanc.
In English you ask someone a question but in Welsh you ask a question to someone. I ask you is Dwi’n gofyn i ti. I ask you something is Dwi’n gofyn rhywbeth i ti. ( i ask something to you)… Normally you say something with somone in Welsh (not to as in English) hence dweud wrthot ti. But you ask to someone gofyn i ti.
The gog types do use ‘gofyn wrth’ when they feel like it, so you have to be careful with them - as usual 
@jan-hutchins - I find older (posher) forms of saying things in English often map quite well to Welsh - think costume drama e.g.
May I ask you?
May I ask something of you?
As per the explanation above Mae indicates the present tense when talking about a thing or a third person.
Mae’r ci yn yr ardd. The dog is in the garden
Mae ci yn yr ardd. There is a dog in the garden
So Mae does not mean ‘there’ in itself - but if there is no ‘the’ in the sentence - then the equivalent English translation has it - if you understand what I mean!
Rich 
In fact, in colloquial Welsh, particularly in the north, people might throw a there (yna) in for good measure:
Mae 'na gi yn yr ardd. (note that the sound at the end of yna causes the beginning of the following word to go all soft)
Thanks Darian and Rich for your prompt response to my questions. This is now a little clearer to me.
Diolch yn fawr
Jan