Taktiken bygger på lagkamratens strategi.

Not literally. In this sentence, bygger på is an idiomatic expression meaning is based on, depends on, or rests on.

So:

• Taktiken bygger på ... = The tactic is based on ...

Swedish often uses bygga på in abstract contexts, not just for physical building.

Examples:

• Teorin bygger på forskning. = The theory is based on research.
• Planen bygger på erfarenhet. = The plan is based on experience.

Because bygga på is a fixed verb + preposition combination in this meaning.

• bygga = to build
• bygga på = to be based on / to build on

You usually have to learn this as one unit. English learners often want to translate word by word, but here the preposition is part of the expression.

So:

• bygger på lagkamratens strategi = is based on the teammate’s strategy

Because -en at the end marks the definite form.

The base noun is:

• en taktik = a tactic

The definite form is:

• taktiken = the tactic

This is very common in Swedish: instead of a separate word like the, Swedish often adds the definite ending to the noun.

More examples:

• en plan → planen = the plan
• en strategi → strategin = the strategy

Because it contains both the definite form and the genitive -s.

Breakdown:

• en lagkamrat = a teammate
• lagkamraten = the teammate
• lagkamratens = the teammate’s

So the ending -s works like English apostrophe + s.

This makes:

• lagkamratens strategi = the teammate’s strategy

This is a very important Swedish pattern.

When a noun is owned by something, the possessed noun is usually not made definite with a separate definite ending.

So Swedish says:

• lagkamratens strategi = the teammate’s strategy

not:

• lagkamratens strategin ❌

The whole phrase is already definite because of the possessor.

Compare:

• strategin = the strategy
• lagkamratens strategi = the teammate’s strategy

The same thing happens in:

• kvinnans bil = the woman’s car
• lärarens bok = the teacher’s book

Not usually in this form.

• lagkamratens specifically means the teammate’s
• en lagkamrats means a teammate’s

So there is a difference:

• lagkamratens strategi = the teammate’s strategy
• en lagkamrats strategi = a teammate’s strategy

Swedish is being more specific here than English sometimes is.

Because bygger is the present tense form.

• bygga = infinitive, to build
• bygger = present tense, builds / is building

In the sentence:

• Taktiken bygger på lagkamratens strategi.

the subject is Taktiken, so the sentence needs a finite verb, and bygger is that form.

A literal structure would be:

• The tactic builds/is based on the teammate’s strategy

This sentence has normal Swedish main-clause word order:

• Taktiken = subject
• bygger = verb
• på lagkamratens strategi = prepositional phrase

So it follows the basic pattern:

• Subject + verb + rest

Swedish main clauses also follow the V2 rule, meaning the finite verb normally comes in the second position.

In this sentence, the subject comes first, so the verb naturally comes second:

• Taktiken bygger ...

It is a compound noun, which is very common in Swedish.

It is made from:

• lag = team
• kamrat = friend / companion / mate

Together:

• lagkamrat = teammate

Swedish forms a lot of nouns this way, by joining words together into one compound.

Because Swedish usually does not use a separate article like the in possessive phrases.

English says:

• the teammate’s strategy

Swedish says:

• lagkamratens strategi

The definiteness is already built into lagkamratens, so no extra word is needed.

This is different from English, where the often still appears in translation.

A simple learner-friendly approximation is:

• TAK-ti-ken BYG-ger po LOHG-kam-rah-tens strah-teh-GEE

A few notes:

• y in bygger is not like English y. It is a front rounded vowel that many learners find tricky.
• å in på sounds roughly like aw in many accents of English.
• g in strategi is pronounced like the y sound in yes in standard Swedish before i, so strategi sounds roughly like stra-te-YEE.

Exact pronunciation varies a bit by dialect, but those points help a lot.