Det er let at gå videre, når man først forstår reglen.

Here det is a formal subject, just like English it in It is easy to.... It does not point to a specific thing. Danish often uses det er + adjective + at-infinitive:

Det er let at gå videre.
= It is easy to move on / continue.

So det is there because Danish needs a subject in the sentence.

Here let means easy.

Danish let can also mean light in other contexts, so the meaning depends on the sentence. In Det er let at gå videre, it clearly means easy.

A close synonym is nemt, so Det er nemt at gå videre would also be possible.

Because at gå is the infinitive, meaning to go.

After expressions like det er let or det er svært, Danish normally uses at + infinitive:

• Det er let at forstå. = It is easy to understand.
• Det er svært at vente. = It is hard to wait.

So at gå videre means to move on / to continue.

Literally, gå means go or walk, and videre means further / onward. But together, gå videre is often idiomatic and means things like:

• move on
• continue
• go on to the next step

So in this sentence it is probably not about physically walking. It is more about progressing once you understand the rule.

Når is the natural choice here because it introduces a general or repeatable situation, often like English when or once.

So:

når man først forstår reglen
= when / once you understand the rule

Why not the others?

• da is usually used for a specific event in the past: when that happened
• hvis means if, so it sounds more conditional and less certain

This sentence expresses a general truth, so når fits best.

In Danish, man often means one, you, or people in general.

So når man først forstår reglen means something like:

• when you understand the rule
• once one understands the rule
• once people understand the rule

Using man makes the statement general, not aimed at one specific person. English often uses you in this kind of general statement, but Danish frequently uses man.

Yes, først often means first, but in this pattern it has a slightly different effect.

In når man først forstår reglen, først adds the sense of once you actually get to that point or once you finally understand it.

So the sentence is not really about doing things in numerical order. It is closer to:

• once you understand the rule
• once you’ve got the rule

Without først, the sentence would still make sense:

Det er let at gå videre, når man forstår reglen.

But først makes it more natural and emphasizes that understanding the rule is the key turning point.

Because når man først forstår reglen is a subordinate clause, and Danish often places certain adverbs, including words like ikke, bare, jo, and often først, before the finite verb in subordinate clauses.

So after når, the order becomes:

• man = subject
• først = adverb
• forstår = finite verb

This word order is very typical in Danish subordinate clauses.

Also, in this sentence først is part of the idiomatic feeling of once rather than simply first.

Because Danish often uses the present tense for general truths and situations that are not tied to one specific time.

So når man først forstår reglen does not mean only when one is understanding it right now. It means something more general:

whenever / once someone understands the rule

English does this too in many cases:

• When you understand the rule, it gets easier.

So the present tense is completely natural here.

Reglen means the rule.

The base noun is regel = rule.
Danish often forms the definite singular by adding an ending to the noun instead of using a separate word like the.

So:

• en regel = a rule
• reglen = the rule

This is a very important Danish pattern.

Because når man først forstår reglen is a subordinate clause, and standard Danish spelling normally puts a comma before subordinate clauses.

So the comma helps show the structure:

• main clause: Det er let at gå videre
• subordinate clause: når man først forstår reglen

English comma use is less consistent in similar sentences, so this often stands out to English-speaking learners.

Yes, absolutely. That is often a very natural English rendering.

Even though når often means when, the combination når man først... very often feels like once... in English.

So a natural translation could be:

Once you understand the rule, it’s easy to move on.

That captures both the grammar and the feel of the Danish sentence very well.