2G Rear Bumper/Taillights Gap

[Volkan-Eclipse]

Hey guys as you can see on the Picture i noticed this ugly gap between my tailights/rear bumper This migh't be a dumb question but does anyone know how this happens and also how i can fix it? i've never removed the rear bumper or taillights on that car i think the gap came after a friend of mine did some rust work on the wheelhouse and after that i just noticed that..

also you can pretty sure see those rusty bolts could they be the problem? also which size are they?

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Thanks guys!
sorry for my bad english greetings from Germany

 

[FIBA M - EC17PSE]

Those bolts are an M6 normal thread pitch, as for the gap it could be the bumper crash bar which also acts as a support, best thing is to remove the tail lights and undo the bolts and see if it moves up some, there is a small metal piece thats on the car and its kinds flimsy so it may have just bent down and is easily bent back up but the bumper needs to be removed ideally for this