Vi planerar projektet tillsammans på datorn.

Because -et is the definite article attached to the end of the noun.

• ett projekt = a project
• projektet = the project

Swedish usually puts the definite article at the end of the noun instead of using a separate word like the in English.

In Swedish, the definite article is often a suffix.

So instead of saying something like the project, Swedish says projektet.

This is very common:

• en bok = a book
• boken = the book
• ett hus = a house
• huset = the house

Since projekt is an ett-word, its definite singular form is projektet.

Planerar is the present tense of planera.

• att planera = to plan
• planerar = plan / am planning / are planning / is planning

A very important point for English speakers: Swedish verbs do not change depending on the subject.

So you get:

• jag planerar = I plan / I am planning
• du planerar = you plan / you are planning
• vi planerar = we plan / we are planning

The verb form stays the same.

It can mean both, depending on context.

Swedish often uses the simple present where English might use either:

• We plan the project
• We are planning the project

So Vi planerar projektet can match either of those in English. Context tells you which one sounds most natural.

Tillsammans means together, and here it works as an adverb.

In this sentence, the neutral and natural order is:

• Vi planerar projektet tillsammans på datorn.

That puts the object projektet first, then the adverb tillsammans, then the prepositional phrase på datorn.

You may hear slightly different word orders in real speech, but this version is very standard and natural.

Usually, yes. Tillsammans means together in the sense of doing something jointly.

Examples:

• Vi arbetar tillsammans. = We work together.
• De bor tillsammans. = They live together.

In your sentence, it tells us that we are planning the project jointly, not separately.

Because Swedish normally says på datorn when talking about doing something on the computer.

So:

• på datorn = on the computer / using the computer

For an English speaker, this is worth learning as a fixed expression. Even though i often means in, Swedish does not usually say i datorn for ordinary computer use.

I datorn would more likely suggest something literally inside the computer, such as files, hardware, or something located internally.

Datorn means the computer.

In many contexts, Swedish prefers the definite form when both speaker and listener understand which computer is meant, or when it refers to the relevant computer being used in the situation.

So:

• på en dator = on a computer
• på datorn = on the computer

In this sentence, på datorn sounds natural because it suggests a specific, understood computer, or simply the computer being used for the task.

Some parts can move, but Swedish has important word order rules.

The basic statement here is:

• Vi planerar projektet tillsammans på datorn.

That is a very natural order:

1. subject: Vi
2. verb: planerar
3. object: projektet
4. adverb: tillsammans
5. prepositional phrase: på datorn

You can move elements for emphasis, but then Swedish usually follows the V2 rule: the finite verb still comes second.

For example:

• Tillsammans planerar vi projektet på datorn.

Here tillsammans comes first, so planerar must still stay in the second position.

V2 means verb-second. In Swedish main clauses, the finite verb usually comes in the second position.

Compare:

• Vi planerar projektet tillsammans på datorn.
• Idag planerar vi projektet tillsammans på datorn.
• Tillsammans planerar vi projektet på datorn.

In all of these, the finite verb planerar is still second.

This is one of the most important Swedish word order rules and often feels unfamiliar to native English speakers.

It is understandable, but it is not the most natural neutral word order.

The more natural version is:

• Vi planerar projektet tillsammans.

Swedish usually prefers the direct object projektet before this kind of adverb in a simple sentence like this.

So for a learner, Vi planerar projektet tillsammans på datorn is the safer and more natural pattern.

Normally, no. Swedish usually requires the subject to be stated.

So you say:

• Vi planerar ... = We are planning ...

You would not normally just say Planerar projektet tillsammans på datorn as a complete standard sentence, because it is missing the subject.

This is different from some languages that allow subject pronouns to be omitted more freely.

You usually learn the gender together with the noun:

• ett projekt

That tells you it is a neuter noun (an ett-word), not a common gender noun (an en-word).

That matters because it affects the article and the definite form:

• ett projekt
• projektet

If it were an en-word, the definite singular would usually end in -en instead.