center text in flexbox that are subcontainer of bootstrap row : wondering if someone can help to center text on about page within body, without changing dynamic page height calculation.

here is page:
https://protasov.by/contacts/

here is jade/pug code

     section.container-fluid
                .row(style="padding-top:20px;").centered-form.center-block
                    section.container(style="display: flex; align-items: center; justify-content: center;").col-md-10.text-center
                        .wb-stl-normal(style="margin: auto; align-self: center;")
                            p
                                em TEXT
                                |  TEXT TEXT
                                br
                                span.wb-stl-small TEXT TEXT
                            br

I tried different approaches and can't achieve any visible result that will center text inside block section.container-fluid so that it be perfectly fill central page space canvas.
