Learn Dutch: Ik bel vandaag de arts. - I am calling the doctor today.

To find the "I" form (the stem) of bellen, we take off the -en, leaving bell. However, Dutch words never end in a double identical consonant. We drop the extra l to get bel. The e still sounds short because the word ends in a consonant, which makes it a "closed" syllable.

Why does vandaag come before de arts instead of at the end of the sentence?

In Dutch, expressions of time (like vandaag) usually sit right after the verb. While English puts "today" at the very end of the sentence, Dutch places time words before the direct object (de arts).

The translation says "I am calling", but isn't bel just "I call"?

Dutch doesn't use an "am -ing" form the same way English does. The simple present tense ik bel translates to both "I call" and "I am calling", depending on what makes the most sense in English.

What is the difference between arts and dokter?

Both mean "doctor" and mean the same thing here. Arts is a bit more formal and is often used as a building block for specialist names, like tandarts (dentist, literally "tooth doctor"). Dokter is more conversational and is the word you use when speaking directly to a doctor.