Hi,

Please go to Appearance → Customize → Custom CSS then add the following custom CSS code:

#main form button,
#main form input[type="submit"] {
    text-transform: uppercase;
    font-family: "Raleway", sans-serif;
    font-weight: bold;
    background: #F5F5F5;
    border-radius: 0;
    font-size: 14px;
    color: #313131;
    padding: 12px 20px;
    display: inline-block;
    -o-transition: .3s;
    -moz-transition: .3s;
    -webkit-transition: .3s;
    transition: .3s;
    cursor: pointer;
    width: auto;
    min-width: 120px;
    text-align: center;
    margin: 0;
    border: none;
}
#main form textarea {
    padding: 15px 20px;
    border: 1px solid #DEDEDE;
    width: 100%;
    height: 120px;
    font-size: 14px;
    color: #313131;
    margin-bottom: 28px;
    line-height: 20px;
    font-weight: 500;
    outline: none;
    vertical-align: top;
}
#main form input[type="text"],
#main form input[type="email"],
#main form input[type="password"],
#main form input[type="number"],
#main form input[type="select"] {
    padding: 12px 20px;
    max-width: 100%;
    border: 1px solid #DEDEDE;
    margin-bottom: 28px;
    font-size: 14px;
    width: 100%;
    font-weight: normal;
    font-family: 'PT Serif', serif;
    max-height: 50px;
    background: none;
}

Regards,
PenciDesign.