There is no button in the app for closing or deleting your account — email your request to [email protected].
Settings → My Account shows only your company, your role, the app language and Change password; a close-account option appears neither there nor anywhere else in the app.
In your email, include the account's email address, your company name and what you want closed. If you also want your personal data erased, say so explicitly — MarbleMap processes personal data under GDPR/KVKK, and erasure requests are handled on that basis. If you have a subscription or billing question as well, put it in the same email.
Two things to finish first: close out your open demands and any offer or order still in progress, because your conversations with the other side end once the account is closed. Also save copies of the offer and contract records you want to keep.
If the real issue is the volume of notifications, you can trim your preferences under Settings → Notifications, and change the interface language under Settings → My Account. Closing the account is the last step, not the first.
Also asked as: How do I delete my account? · I want to cancel my membership, how? · How do I request erasure of my personal data? · Where is the delete account button?