Vielleicht sollten wir doch früher anrufen, um sicherzugehen, dass alles klappt.

Because German main clauses follow the verb-second rule.

In Vielleicht sollten wir ..., Vielleicht takes the first position, so the conjugated verb sollten must come next, in second position. The subject wir comes after that.

So the pattern is:

Vielleicht + sollten + wir + ...

Compare:

• Wir sollten früher anrufen.
• Vielleicht sollten wir früher anrufen.

Both are correct; the word in first position changes, but the finite verb still stays second.

Yes, it is very close to English should here.

sollten expresses a suggestion, recommendation, or a tentative idea, not a strict obligation.

So this sounds like:

• We should call earlier
• not We must call earlier

It is softer than müssen.

Also, sollten is the Konjunktiv II form of sollen, which often makes a suggestion sound more polite or less direct.

doch is one of those very common German words that adds nuance rather than a simple dictionary meaning.

In this sentence, doch suggests something like:

• after all
• actually
• maybe after all
• contrary to what we were thinking before

So Vielleicht sollten wir doch früher anrufen implies that maybe the speaker is reconsidering an earlier plan, for example:

• maybe they were going to call later,
• but now they think calling earlier might be better.

It adds a slight sense of change of mind or contrast with a previous idea.

Because früher means earlier, while früh means early.

Here the idea is comparative: calling earlier than originally planned.

• früh anrufen = call early
• früher anrufen = call earlier

So früher does not necessarily mean early in the day. It just means before the time we were otherwise thinking of.

Because sollten is a modal verb, and with modal verbs the main verb usually appears in the infinitive at the end of the clause.

So:

• Wir sollten anrufen.
• Vielleicht sollten wir früher anrufen.

This is a very common German pattern:

• Ich will gehen.
• Wir müssen warten.
• Sie kann kommen.

The conjugated modal verb comes earlier, and the other verb goes to the end.

Yes, anrufen is a separable verb.

When it is conjugated by itself in a main clause, it splits:

• Wir rufen früher an.

But when it stays in the infinitive, as it does after a modal verb, it does not split:

• Wir sollten früher anrufen.

So:

• finite form: rufen ... an
• infinitive form: anrufen

um ... zu introduces a purpose clause, meaning in order to.

So um sicherzugehen means:

• in order to make sure

The expression comes from sichergehen in the sense of to make sure / to be certain.

In modern spelling, when this expression has that figurative meaning, it is normally written together here as sicherzugehen.

So the structure is:

• um
  • infinitive with zu

Example:

• Wir rufen früher an, um sicherzugehen ...
• We’re calling earlier in order to make sure ...

Because the sentence needs to state what we want to make sure of.

dass alles klappt tells us the content of that idea:

• to make sure that everything works out

So:

• um sicherzugehen = in order to make sure
• dass alles klappt = that everything works out

This is a very common pattern in German:

• Ich möchte sicherstellen, dass ...
• Wir wollen sichergehen, dass ...

Because dass introduces a subordinate clause, and in German subordinate clauses the conjugated verb usually goes to the end.

So:

• main clause: Vielleicht sollten wir ...
• subordinate clause: dass alles klappt

The structure is:

dass + subject/object/etc. + verb

Examples:

• dass alles klappt
• dass er morgen kommt
• dass wir genug Zeit haben

This verb-final word order is one of the most important patterns in German.

klappen here means something like:

• to work
• to work out
• to go smoothly
• to turn out successfully

So dass alles klappt means that everything goes according to plan.

It is a very natural everyday verb in German.

For example:

• Hoffentlich klappt alles. = Hopefully everything works out.
• Der Plan hat nicht geklappt. = The plan didn’t work out.

German uses commas to separate certain kinds of clauses, and both of these are cases where a comma is required.

1. before um sicherzugehen

   • because um ... zu introduces an infinitive clause

2. before dass alles klappt

   • because dass introduces a subordinate clause

So the commas are not optional here; they are part of standard German punctuation.

Yes, both make the statement softer, but in slightly different ways.

• Vielleicht = maybe / perhaps
• sollten = should, a tentative suggestion

Together they make the sentence sound especially careful and non-pushy, something like:

• Maybe we should call earlier after all ...

So the speaker is not giving a hard command. They are politely floating an idea.