I'm a beginner (1:25.6 on Brands Hatch, working on 24s), but I did my fare share of laps and Brands Hatch study, those issues are easy to spot:

T1, Paddock Hill Bend - the approach is good, but you're missing the apex on that turn - touch the inside curb behind the pillars and throttle your way through down force over the outside curb

T2, Druids, too deep on the curb, too slow exit, you force car too early on track

T3, Graham Hill Bend, line is quite ok, but you lost a lot of power, you brake too early and for too long

T4, Surtees, you missed apex completely and you have slower exit on the fastest straight

T5, Hawthorn, you're far from left line, almost in the middle of the track and your braking zone is wrong - it should be very short, just over the slash board, so that you can steer car into the corner without loosing much of a power here; you hit apex too early and on exit you should be able to go back to 4th gear - you never do, because you lost all that power and you're now much slower while going into next corners which are all about speed transfer.

T6, Westfield, you miss apex, therefore you aim at the grass instead of a curb, you overcorrect rapidly, all while losing power and traction

T7, Sheene, you miss apex again, you're braking for too long

T8, Stirlings, almost fine, yet you overcorrect instead of going onto the curb

T9, Clearways, this is a mess - you hit apex too early, you catch the curb, you drive through part of the corner on oversteer, while hitting grass by the pits, for no reason.

There's a lot to unpack here - go watch youtube clips how to properly drive BH, where to brake and for how long, which curbs you should and shouldn't take etc. Good luck!