garantieren
to guarantee
To firmly assure or promise that something specific will happen or be the case.
Ich kann dir nicht garantieren, dass wir die Karten noch bekommen.
I can't guarantee you that we'll still get the tickets.

to guarantee
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to guarantee
To firmly assure or promise that something specific will happen or be the case.
Ich kann dir nicht garantieren, dass wir die Karten noch bekommen.
I can't guarantee you that we'll still get the tickets.

The ending '-ieren' often indicates a word from another language. Such verbs are always regular and form the perfect tense with 'haben' (to have) and the participle ending in '-t' (garantiert).
Er hat mir garantiert, dass er pünktlich sein wird.
He guaranteed me that he would be on time.
'Garantieren' (to guarantee) is often used with two objects: The person to whom something is guaranteed is in the dative, and the thing that is guaranteed is in the accusative.
Der Verkäufer garantiert dem Kunden eine schnelle Lieferung.
The salesperson guarantees the customer fast delivery.
'Garantieren' (to guarantee) is very often used with a subordinate clause that begins with 'dass' (that). This explains the promise or assurance more precisely.
Wir können garantieren, dass Ihre Daten sicher sind.
We can guarantee that your data is secure.
When it comes to liability for a product, the preposition 'für' + accusative is often used.
Der Handwerker garantiert für die Qualität seiner Arbeit.
The craftsman guarantees the quality of his work.
to promise
'garantieren' and 'versprechen' both mean that someone assures that something will happen or is true. 'versprechen' is very common in everyday language and personal: you tell someone that you will do something. 'garantieren' sounds stronger and more binding. It fits well when you are very sure or take responsibility for a result. Learners may confuse the words because both express an assurance. As a simple guideline: a person can promise something; someone who guarantees something sounds more certain and often somewhat more official.

Der Händler garantiert, dass das Gerät zwei Jahre funktioniert.
The dealer guarantees that the device will work for two years.
Die Mitarbeiterin verspricht, die Unterlagen heute noch zu schicken.
The employee promises to send the documents today.