Learn Portuguese (Portugal): A burocracia é complicada, portanto eu preencho o formulário. - The bureaucracy is complicated, therefore I fill out the form.

No, the verb complicar (to complicate) only has one regular past participle: complicado. Here, it acts as an adjective describing the feminine noun a burocracia, which is why it ends in -a. Unlike verbs such as pagar or aceitar that you are learning in this lesson, complicar does not have a special short form.

Does the verb preencher have a short past participle like other verbs in this lesson?

No, preencher (to fill out) is entirely regular in its past participle, which is preenchido. You will use preenchido for all perfect tenses and passive voices. In this specific sentence, however, preencho is just the present tense eu (I) form.

Is portanto interchangeable with então?

They are very similar and both mean 'so' or 'therefore' in this context. Portanto sounds slightly more formal or conclusive (therefore), while então is very common in everyday spoken Portuguese (so). Using portanto here fits well with the slightly formal topic of bureaucracy.

Why is it a burocracia é complicada instead of a burocracia está complicada?