Hello and welcome to this unique community, Ivan.
Being a vocal student myself I can assure you that you must find a different way of producing your sound. You must feel it yourself, that you don't have a lot of flexibility in your singing. I wouldn't worry though, there are going to be many frustrating hours before you find a better sound and then there will be even more hours until you find an even better sound and so it will go on for as long as you sing.
I recommend you to listen a lot to good baroque singers ( you can find recordings in the video section ). You should listen with great attention again and again to try and identify how the singer is producing his sound. I personally learn a lot by listening and imitating what I hear with as much precision as possible. I also think it'd be ideal that you wait with singing words for a good while and only use vowels for vocal production.