Large-Format Photo Resolution Enhancement

I have a small batch—no more than ten images—that must look razor-sharp when printed at a huge 160 × 230 cm final size. The originals aren’t currently up to that standard, so I need someone who can carefully... (Budget: €8 - €30 EUR, Jobs: Graphic Design, Illustrator, Image Processing, Image Upscaling, PDF, Photo Editing, Photoshop, Print Design)