Theme Changes With Figma, Adobe Etc


I am discussing with someone who would do design modification on my theme using figma, Adobe xd etc .he says there are minor layout problems.He say he can create a better layout and fix the small problems here and there. Other than that could also do a different design, that then a front developer could integrate the figma, adobe file

But I dont see how it would work ? or how it would sit in my back end ?

My current theme is great but there are details that bothers me and i need someone with the same vision i have , that would understand how i need things to look. but I dont see how it would integrate with my current website or even replace it ? I am concerned about the codes, hooks etc

thank you

After the new design is created, you should find front-end developer. He will integrate new look and feel to your website. It can be made within separate theme. Existent hooks can be saved without big problems