Extend wiring in the middle of a run??

I’m about to do a kitchen renovation and need to extend some electrical wiring but need to do it in the middle of the run? Is it as simple as cutting the wiring and just adding more in? As an added layer of protection I would cover the added in section with conduit. Is this safe to do?

As another added challenge, all of the wiring is aluminum as this house was built in 1970. Also curious if it would be possible/safe to make this extension with copper wiring? I assume that would mean that I would have to pigtail all of the added connections as well. All of the outlets and switches in the house have already been pigtailed to copper at the ends. Just wondering if it would be safe to do the extension in the middle of the aluminum run with copper wiring or if it would be best to keep the entire run aluminum.

Any insight is appreciated. Thank you!