How can I change the harddisk?

Given the propriety and end-user non-upgradability of these MacBook/Pro

and MacBook/Air models ~ with certain connectors and blade-like storage..

Not for the neophyte DIY'er. ~ You may find AASP that'd use OWC parts.

..You may have a harder time with upgrades to storage capacities.

Within time this thread came to be posted, several things I've learned

and some factoids were hidden. (As volunteer here, time has no value.)

OWC Aura Pro X2 NVMe – PCIe 3.1 x4 SSD.

[Numbers I found in duckduckgo search, incl. DIY sites]

SSD upgrades in this category example fit 2013-2015

and their link to see that items specs is here in blue.

Usually one would need kit option from OWC, may have plastic pry

tool, a few small screwdrivers, an external SSD enclosure for new

SSD (to transfer from your live Mac's SSD) And then replace Mac

internal storage SSD with new upgrade part. By now this would

have either a copy clone on its SSD; it would be ready to boot MB.

Use older SSD as extra external storage, with enclosure from OWC.

Kit should include install instructions; on paper with parts/tools.

And also may include link to OWC to view installer video files.

Only part# near your model, works with the following Model IDs

OWC Solid State Drives

For MacBook Pro with Retina Display (Late 2013 - 2015)

https://eshop.macsales.com/shop/ssd/owc/macbook-pro-retina-display/2013-2014-2015

• MacBookPro11,1
• MacBookPro11,2
• MacBookPro11,3
• MacBookPro11,4
• MacBookPro11,5
• MacBookPro12,1

• OWC Aura SSD for Mid-2013 or Later Mac - OWC Digital

https://www.owcdigital.com/products/aura-ssd

This is only an Example. Their cost estimate for 2GB of OWC item

with the external enclosure and kit runs near $430+ shipping.

Perhaps this may be an answer; or get external enclosed SSD

or larger drive enclosure (self-powered) of suitable standard.

MacBook Pro 2017 flash storage is soldered to the mainboard, so... no. Not without re-soldering.