Der Tisch wackelt ein bisschen, wenn man sich darauf stützt.

Because der Tisch is the subject of the sentence — it is the thing doing the action wackelt.

• der Tisch = nominative case
• den Tisch = accusative case

Here, the table is the thing that wobbles, so German uses the nominative: Der Tisch wackelt.

If you said den Tisch, that would make it sound like the table is a direct object, which it is not here.

wackelt comes from wackeln, which means to wobble, to shake a little, or to be unsteady.

For a table, wackeln suggests that it is not stable and moves slightly when pressure is put on it.

So it is not a dramatic shaking — just a small unstable movement.

Compare:

• Der Tisch wackelt. = The table wobbles.
• Der Tisch ist wackelig. = The table is wobbly.

The first describes the movement; the second describes the table’s quality.

ein bisschen means a little bit.

It works here as an adverbial expression modifying wackelt:

• wackelt ein bisschen = wobbles a little

You could also hear:

• ein wenig
• etwas

All of these can mean a little.

ein bisschen is very common and natural in everyday German.

Here wenn introduces a condition or repeated situation.

In English, depending on context, it can be translated as:

• when
• whenever
• sometimes if

In this sentence, it has a general meaning:

• whenever someone leans on it, the table wobbles a little

So wenn is not necessarily talking about one single future moment. It often describes something that happens regularly or under a certain condition.

man is the German impersonal subject. It often means:

• one
• you
• people
• someone

In natural English, we usually do not translate it as one, even though that is the closest literal match.

So:

• wenn man sich darauf stützt
  = when you lean on it / when someone leans on it / when people lean on it

Also notice that man always takes third-person singular verb forms:

• man stützt
• not man stützen

Because sich stützen is a reflexive construction.

The verb stützen by itself can mean to support something:

• Er stützt den Schrank. = He supports the cabinet.

But sich auf etwas stützen means:

• to support oneself on something
• to lean on something

So in this sentence:

• man stützt sich darauf
  literally = one supports oneself on it
  naturally = one leans on it

The sich is necessary because the person is using the table to support themselves.

Because once der Tisch has already been mentioned, German often uses a da-compound to refer back to it.

• darauf = on it
• literally: da + auf

German commonly uses forms like darauf, damit, davon, darüber, etc. when referring to things rather than people.

So instead of repeating auf den Tisch, German says darauf.

If you wanted to repeat the noun, you could say:

• wenn man sich auf den Tisch stützt

That is also grammatically correct, just less compact.

For things, German usually prefers da- + preposition forms rather than a preposition plus a personal pronoun.

So for a table, German normally says:

• darauf = on it

rather than:

• auf ihn

Even though Tisch is grammatically masculine, it is still an object, not a person. That is why darauf sounds more natural.

With people, you would normally use the preposition + pronoun form:

• auf ihn
• auf sie

But for objects, darauf is the standard choice.

With sich stützen auf, German uses accusative.

So if you used the full noun instead of darauf, you would say:

• sich auf den Tisch stützen

not:

• sich auf dem Tisch stützen

This can be confusing because auf is a two-way preposition and can take either accusative or dative in other contexts. But with this verb, the standard construction is:

• sich auf + accusative stützen

So it is best learned as a verb pattern.

Because wenn man sich darauf stützt is a subordinate clause introduced by wenn.

In German subordinate clauses, the finite verb goes to the end.

So the order is:

• wenn
  • subject + other elements + verb

Here:

• wenn
• man
• sich
• darauf
• stützt

This is one of the most important German word-order rules.

That order is natural because German tends to place short pronouns early in the middle of the clause.

So in:

• wenn man sich darauf stützt

you have:

• man = subject
• sich = reflexive pronoun
• darauf = prepositional adverb
• stützt = verb at the end

This is a very typical German pattern.

You may see some variation in more complex sentences, but man sich darauf stützt is the normal, straightforward order.

Yes, absolutely.

German can put the wenn-clause first or second.

So both are correct:

• Der Tisch wackelt ein bisschen, wenn man sich darauf stützt.
• Wenn man sich darauf stützt, wackelt der Tisch ein bisschen.

If the subordinate clause comes first, the main clause still follows the verb-second rule, so the finite verb comes immediately after that whole first clause:

• Wenn man sich darauf stützt, wackelt der Tisch ein bisschen.

Not:

• Wenn man sich darauf stützt, der Tisch wackelt ein bisschen.

Yes, but it is not exactly the same.

• Der Tisch wackelt ein bisschen focuses on the movement.
• Der Tisch ist ein bisschen wackelig focuses on the property of the table.

So:

• wackelt = it actually wobbles
• ist wackelig = it is somewhat unstable / wobbly

In your sentence, wackelt fits well because the wobbling happens specifically when someone leans on it.

Yes. German often uses the present tense for things that are generally true, habitual, or normally happen under certain conditions.

So this sentence means something like:

• the table wobbles a little whenever someone leans on it

It is not limited to one moment happening right now. It describes a typical behavior of the table.