Rita Rossweisse - SecondKeyManga

Help me to finish it !!

I need a hand here. She's Rita Rossweisse from Honkai Impact 3rd, but this is the battlesuit she on use on the manga called The Second Key. In that manga, she is a version of Kevin Kaslana, and I really love how she looks in it. The part where I found difficult, is on the weapon, but I really appreciate any advice or help in any other thing.