What class are you looking to fly? This is what I found for your requested flight numbers (there are some other options involving Egypt Air or Ethiopian)
Jul 7 27.5k + 153,22€ (PEco on SN481)

Business is not available on your dates on those flights, there is some availability on Ethiopian with lengthy and not very straightforward routings (e.g. involving airport changes)
Jul 7 37.5k + 332,57€ (Business, however you'd take SN2618 from FRA to BRU and would be on SN481 only the next day, Jul 8)
Jul 8 37.5k + 216,22€ (Business on SN481)

Business on the return (there are also Eco and PEco Options):
Jul 13 54588 + 222,10$ on LH591
No availability on SN482, but:
Jul 13 37500 + 252,60$ on SN491 and SN2609 (NBO-BRU-FRA)
Jul 13 37500 + 222,40$ on SN491 to BRU
more options with other airlines, cheapest being Ethiopian with 37.5k + 75$.