How to pronounce "sheet" properly? [duplicate]
It sounds like your KIT and FLEECE vowels aren’t far enough apart.
The difference is that the KIT vowel is /ɪ/, and the FLEECE vowel is /iː/, with a bit of length added to it, too.
The KIT vowel is a little bit more open and a little bit further back than the FLEECE vowel:
Many minimal pairs exist for these two, with bit and beet perhaps the most often cited.
This is an error sometimes made by Spanish speakers in English. I am guessing that your first language does not consider the KIT and FLEECE vowels to be distinct phonemes the way English does.