Pronouncing the "-ed" ending in English verbs can indeed be a bit tricky, as it can sound differently depending on the letter before it. But don't worry; it's all based on 3 simple rules.
The three sounds are:
If the verb has a "d" or a "t" sound just before "ed," then you pronounce it as "id".
If the verb doesn't have these sounds, don't pronounce an extra syllable.
For instance, the regular verb "decided" is pronounced "decide-id" despite de fact that the verb "decide" ends in the letter "e", We don't pronounce the letter "e", so the last sound of this word is "d".
Examples:
2. If the verb before "ed" ends in the following sounds 'p', 'f', 's', 'ch', 'sh', and 'k', the "ed" must be pronounced like "t".
Examples:
3. For all other verbs where you can't apply rule #1 or rule #2, "ed" is pronounced "d".
Examples: