German · Pronunciation Guide
SHLEE-sn. sch is sh, ie is a long 'ee', and the ß is a plain hissing s.
First syllable, with the long 'ee' carrying real duration. The ß is doing double duty as a stress cue: because it only appears after long vowels, seeing it tells you the stressed syllable is a long one, which is useful when you meet an unfamiliar word on the page.
Listen: schließen
Free browser voice. Hear it read by a real native speaker inside the LingoDrop app.
Bitte schließ die Tür.
Please close the door.
Listen: Bitte schließ die Tür.
Free browser voice. Hear it read by a real native speaker inside the LingoDrop app.
Bitte schließ die Tür drops the -e from the imperative, which is the ordinary spoken form — schließe would sound formal or written. Tür holds the long front-rounded ü followed by the vocalised r, so the sentence ends on one of German's harder vowels with nothing after it to hide behind.
Two written characters mislead. The ß gets read as a capital B by newcomers, and the schl cluster gets simplified to 'sl'. Both are worth attacking directly: ß is an s, and the cluster needs the sh held before the l arrives. Beyond that, keep the vowel long — the ß is telling you so, and shortening it makes the word sound clipped.