Iget an error

Opening and ending tag mismatch: _cript line 5 and script, line 13, column 26Opening and ending tag mismatch: _cript line 5 and script, line 13, column 26 

Thanks Ermin for your reply and your time. 

About the Size

The logo i uploaded was 394 × 252, so way under these dimension. 

About customising

I have tried the "customize" menu but the code has changed a lot between version 10 and 11.

In Main Layout view I cannot find the following container, which helps control the size of the nav bar header.

In Main Layout view, here is the code existing in Version 10 but absent in version 11

<div id="wrapwrap" t-att-class="pageName or ''">
            <header>
                <div class="navbar navbar-default navbar-static-top" style="height:100px">
                    <div class="container">
                        <div class="navbar-header" style="margin-top:-17px">

In Show Logo view: When changing the logo size, there is no effect on the size.

I version 10,  I change the logo size in Show Logo Layout and  change the nav bar size in Main Layout to adjust for the new size.

but i cannot do the same in version 11. 

Any thoughts about this issue?

First of all, check if your logo has a width of less than 1024 pixel, if it has more, it will automatically get squared and therefore very small on the website.