'laga mat' is being used inconsistently in this course (my opinion); it is confusing. Kan) instead? Is it inextricably linked to 'mat' in Swedish? Polish, English, German, French - no need to add food to "gotować," "cook," "kochen," "cuisiner" - is Swedish just a unicorn in this respect?
It's a quirk of idiomatics. The direct English equivalent to 'att laga mat' is 'to make food', which is actually pretty common in American English if you replace 'food' with a more specific word describing what type of food is being made (for example 'I made soup.' or 'I made salad.'). Swedish does not (as far as I can tell) have a simple verb that means 'cook' in the generic sense like can be found in English, German, and most Italic languages, so they use this phrasal verb instead.
Just 'att laga' by itself means 'to fix' or 'to repair', though in colloquial speech it's sometimes used to refer to cooking as well.