In the first place you may need to draw a sharper line between English and German, because while German uses the subjunctive (K1) for reported speech, thoughts, etc., English doesn't -- it only uses the backshift in tenses. That is, one tense farther in the past, but still indicative.
(That is, MikeE or someone may have more to say about that from a different grammatical angle, but this terminology is the way I grew up understanding it, and also the way that seems most helpful to me in comparing tenses and moods with the corresponding ones in Romance languages and Latin, and to some extent German.)
You can also use 'would' for reported speech, but it's not the only option. For example,
He said, "I'm going shopping."
He said he was going shopping.
He said he would go shopping.
Liesl thought he was going shopping.
Liesl thought he would go shopping.
There's not much you can do to make that more future, except perhaps add another 'go.'
He said "I'm going to go shopping tomorrow."
He said he was going to go shopping tomorrow.
Liesl thought he was going to go shopping tomorrow.
Liesl thought he was going to go shopping the next day, but he didn't.
But the 'would' options don't change, and they can also have a future meaning.
English does use the subjunctive for hypothetical conditions in the present or future, or for contrary-to-fact conditions in the past.
If he went shopping (but he might not), he could buy us a present.
If he had gone shopping yesterday (but he didn't), he could have bought us a present.
As you can see, the first of those sentences can have either a present or future meaning. To specify, you have to add a time adverb like 'right now' or 'tomorrow.' That's not unlike German use of the present tense with a future meaning.
English doesn't have future subjunctive forms of the main verb (unlike, say, Portuguese), but we do sometimes use the helping verb 'be' (which does have subjunctive forms) if we want the subjunctive to be more visible. It often also emphasizes the uncertainty, makes the possibility sound less likely.
Who knows -- if (by any chance) he were to go shopping tomorrow, he could buy us a present.
That's the only way to express the future subjunctive in English that I know of. It can be used interchangeably with 'If he went shopping tomomorrow,' but it's less ambiguous because it's only future, not present.
Does that help? (-: