there are 3 main conditionals that you need to operate according to be fulfilled.
We use conditional 1 to express likelyhood, we expect the condition to be fulfilled.
e.g. if i have money, i buy sweets - wenn ich geld habe, ich kaufe bonbons
we use conditional 2 to express conditions which are unlikely to be fulfilled and to express wishes.
e.g. if i had a million pounds, i would by a ferrari - ich viel rech ware, wurde ich einen ferrari kaufen.
If+had/were + would + infinitive
Wenn+hatte/ware + wurde + infinitive
wurde - this means would, it fulfills the condition 100% however we can reduce the unlikelyhood by substituting konnte, meaning could.
conditionals can also be reversed.
conditional 3 - the impossible condition
we use this to express what we would of done in the past of the condition had been available the time in which we could of fulfilled the condition has elapsed and the oppertunity is no longer available. we use it usually when we regret lost oppertunities or to celebrate missed disasters.
e.g. if i had bought the cake, i wouldnt of bought the sandwhich. - wenn ich den kuchen gekauft hatte, hatte ich keinen sandwhich gekauft.
If a modal verb is present in conditional 3 we dont use the past participle, but rather the infinatives of the main verb and the modal.