Jeg følger vejledningen, så jeg ikke laver fejl.

Følger is the present tense form of følge.

• at følge = to follow
• jeg følger = I follow / I am following

In Danish, the present tense is often formed with -r:

• at lave → laver
• at følge → følger

So both verbs in the sentence are in the present tense: følger and laver.

The ending -en makes the noun definite: the guidance / the guide / the instructions.

• en vejledning = a guide / an instruction manual / some guidance
• vejledningen = the guide / the instructions

Danish usually adds the definite article to the end of the noun instead of using a separate word like the.

Also, Danish may use singular vejledningen where English naturally says the instructions. So the grammar is Danish, even if the best English translation sounds plural.

It can mean several closely related things depending on context:

• guidance
• guide
• manual
• instructions

In this sentence, it most naturally refers to some kind of instructions or guidance that the speaker is following. So even if the Danish word is singular, the English meaning may be something like the instructions.

Here så means so that, not just so in the sense of therefore.

It introduces a purpose clause:

• Jeg følger vejledningen, så jeg ikke laver fejl. = I follow the instructions so that I do not make mistakes.

This is different from a simple result statement. In this sentence, the idea is purpose: the speaker follows the instructions in order not to make mistakes.

Because så jeg ikke laver fejl is a subordinate clause.

In Danish subordinate clauses, words like ikke usually come before the finite verb:

• ... så jeg ikke laver fejl

Compare that with a main clause, where ikke usually comes after the finite verb:

• Jeg laver ikke fejl

So the position of ikke is a very useful clue that this part is subordinate.

Because lave fejl is the normal Danish expression for make mistakes.

• at lave en fejl = to make a mistake
• at lave fejl = to make mistakes

Even though English uses make, and learners may expect something like do from other languages, Danish idiomatically uses lave here.
So gøre fejl is not the standard expression.

Because fejl here means mistakes in a general plural sense.

Compare:

• en fejl = a mistake
• fejl = mistakes

So:

• laver en fejl = makes a mistake
• laver fejl = makes mistakes

A useful thing to notice is that fejl has the same form in the plural as in the base noun form, so there is no extra ending here to show the plural.

Because the second part has its own clause, so it needs its own subject.

• Jeg følger vejledningen = one clause
• så jeg ikke laver fejl = another clause

Danish normally does not leave out the subject in a full clause, so you repeat jeg.

The comma is there because the sentence contains a clause introduced by så.

In Danish comma rules, whether this comma is written can depend on which comma system is being used:

• with start comma, you write it:
  Jeg følger vejledningen, så jeg ikke laver fejl.
• without start comma, it may be left out:
  Jeg følger vejledningen så jeg ikke laver fejl.

So the version with the comma is perfectly normal, and many learners will see it written that way.

Yes. A very natural alternative is:

Jeg følger vejledningen for ikke at lave fejl.

That also means I follow the instructions so as not to make mistakes / in order not to make mistakes.

The difference is mostly structural:

• så jeg ikke laver fejl = full clause with subject + verb
• for ikke at lave fejl = infinitive structure

Both are correct and natural.