If you see duplicates for transactions on some accounts, it usually means that these accounts are synced across multiple connections.
To check if your accounts are synced across multiple connections, you can go to the Linked Accounts page. You can access it here from the website or from the app by going to the settings.
If you see that some accounts are synced across multiple connections, you can remove the duplicate connections there.
A credit card is synced
If a credit card is synced, its transactions may come up as well as those of the current account already synced in your Finary.
In that case, you can untick the credit card in the Budget section, under Accounts.
If your card is a deferred debit card and you want to keep the detail of your purchases, see Understanding immediate and deferred debit cards instead.