Translation:I read a newspaper while he cooks.
I noticed that the last 5 syllables of the sentence have the same vowel letter. Amazing! But I hear from 2 to 4 different sounds for those 5 letters. But I'm not sure. Good people, could you please clarify this for me, are the sounds really different there and which is which?
No. The verb lagar in Swedish means mending or fixing and you need to specify what it applies to.
"Jag läser en tidning medan hon lagar bilen." - "I read a newspaper while she repairs the car"
"Jag läser en tidning medan han lagar hålet i skjortan" - "I read a newspaper while he mends the hole in the shirt"
I think of "lagar mat" as "fix food" (or even "make food", which is pretty colloquial (American) English. So I might translate this sentence as "I read the newspaper while he fixes food." (maybe more usual: while he fixes dinner"). Using "cooks" for "lagar mat" makes me ask, is there a difference in Swedish between "to cook" used transitively, and used intransitively? Is th construction different between "he is cooking" and "the porridge is cooking"?
'make food' is usually an accepted translation for laga mat throughout the course, but 'fix food' has an exact translation in fixa mat which is used pretty widely. (even more widely if you use the colloquial word käk for 'food', too). You should try to think of laga mat as 'cook'. :)
The porridge is not 'cooking' in Swedish. If things boil, they kokar, so you can say medan gröten kokar 'while the porridge is cooking' [i.e. boiling], but for food that isn't exactly "boiling" we can either use the passive lagas or tillagas, or some more specific expression. E.g. steken är i ugnen 'the roast is in the oven'.