The Subjunctive Mood is used to report others' words or to present hypothetical situations.
Uses of Subjunctive 1:
Used to report something someone has said, or ask something for somebody.
Uses of Subjunctive 2:
Used to present unreal/hypothetical situations/things or to reflect on something that could've happened.
In the spreadsheet, you will notice that I only included two irregular verbs: haben and sein. This is because these two are the only ones that you'll really need. The subjunctive moods are generally uncommonly used, and I haven't come across many, if any, situations in which I had to use other irregular verbs in subjunctive form.
*As you can see, some of the original conjugations for haben in the subjunctive 1 is the same as forms of haben in the present tense (habe and haben). To 'solve' this issue, you would replace these overlapping conjugations in the subjunctive 1 with the conjugations in subjunctive 2.
For example, if you wanted to report something that your friend had done, you would use subjunctive 1. You're about to use 'habe' in that report (3rd person singular), but you stop yourself- you remember that you have to replace 'habe' with 'hätte' in your report.
If you asked me why this happens, I wouldn't know as of now. If anybody reading knows why there has to be the original conjugations for haben as 'habe' and 'haben' in the subjunctive 1 before switching to subjunctive 2 in just those forms, please let me know.
** For Subjunctive 1 forms of regular verbs, such as können, you will always use the (verb stem) + (verb ending, which is underlined).
*** The Subjunctive 2 forms of regular verbs is the same as the Simple Past conjugations. Some of these verbs that you need to know are könnte, würde, möchte, sollte, & wollte.
Er sagte, er sei krank. --> He said that he was sick.
Er fragte, ob ich geigespielen könne. --> He asked if I could play violin.
When you order things at a restaurant, use 'möchte.'
Ich möchte ein Wasser. --> I would like a water/It would be nice to have a water. (It's generally more polite to use Subjunctive 2 when ordering things from a store/restaurant.)
wenn + (verb in subjunctive 2) to express hypothetical situations
Wenn ich ein Millionär wäre, würde ich in jedes Land gehen. --> If I were a millionaire, I would go to every country.
wenn + (verb in subjunctive 2) + (past participle) to reflect on things that could have happened.
Wenn ich gewusst hätte, dass es regnen wird, würde ich nicht in den Park gegangen. --> If I had known that it was going to rain, I would not have gone to the park.
als (ob) + (verb in subjunctive 2) to say 'as if.'
Er sah aus, als ob er ein Gespenst gesehen hätte. --> He looked as if he had seen a ghost.