"That's often ('tenpo mute la')true" said Dumbledore. He looked grumpily over the top of his half-moon glasses (this cost me --'ilo' for 'ijo' for starters -- a mistake common even with old Esperantists -- and then off on wild tangents from there. This is one of those cases where -- to avoid drowning in 'pi' -- I would recommend fronting the determiners, 'sama', in this case, up to the pre-'pi' head 'ilo lukin sama pi wan mun' or so) "Now ('tenpo ni la'? otherwise not clear) every boy comes to feel that he is very important. In his coming walk (maybe just "travel, journeey" and no 'noka'?), in his coming talk, many people will know about him! Many people will know about him because of events of the past time of his ignorance. Do you know that if Harry becomes great in our absence, he will be very good?
Prof. McGonagall opened here mouth and changed her mind and ate nothing and said "Good. Fortunately you talk well. But, Dumbledore, how did the boy come to be here?" For a little while she looked at Dumbledore's robe. She looked as though she thought that Dumbledore could(might?) have Harry under that robe.
"Hagrid had him and came here"
"Do you think that Hagrid will do well a thing of this importance' (well, 'sama suli ni' -- 'sama' is a preposition -- at least "a thing like this important thing" but maybe also 'ijo suli pi sama ni' "an important thing like this" or even 'ijo pi suli pi sama ni' "a thing of importance similar to this". There are shades here and I am not sure which is which.)
"I think Hagrid wants to do well the thing of my existence" Dumbledore said. (I expected 'ijo pi wile mi' "what I want")
"I didn't say he was happy" said Prof, Mcgonagall, as though she didn't want to say this."But you can't say that he acts as if he didn't want to screw things up. He often ... What's that?"
"until" and "since" are unsolved problems. I think the old suggestion of finally using something other than 'kama' and 'pini' is right and that we start using 'tawa' and 'tan'. So, 'tawa (tenpo) ni: ona li ken awen' or some such.