When we are talking about a situation that is not real, we use a special form
of the verb known as the subjunctive. We use this form, for example, to
express wishes.
der Konjunktiv II: The subjunctive is a verb form that is used to express
something that is not real but is a fantastical proposition. It is used, for
example, to express a wish or a requirement that is unrealistic. It is also
used to ask a favor of someone or to make a proposal in a polite manner.
real: Ich habe keinen eigenen Fahrradladen.
wish: Ich hätte gern einen eigenen Fahrradladen.
The past subjunctive of "haben" is conjugated as follows:
Singular
1st person ich hätte
2nd person du hättest
3rd person er/sie/es/man hätte
Plural
1st person wir hätten
2nd person ihr hättet
3rd person sie hätten
Formal Sie hätten