How do I add an image instead of a text to the main menu that links to a page?

Hi mistermagoo8691 and Rikard,

Thanks for your help!
But unfortunately it doesn’t work. Maybe because I don’t understand it completely :-(
What I did: I copied the code below and changed the image-url.
Also I changed the menu-item, and than placed the code in the Theme General Styling.
But it doesn’t work.
Please help me what to do now?
————
li#menu-item-2935 {
background-image: url(https://www.solveigmalvik.com/wp-content/uploads/2014/09/Danish-flag-300×171.png);
background-size: contain;
background-repeat: no-repeat;
background-position: 50% 50%;
}
li#menu-item-2935 a {
opacity: 0;
}

Hi Rikard,
That’s not my website, but the one from the older tickets. Look, this is my code I placed in the Them options. On my website you can see the same image in the footer (the english flag).
http://www.off-thegrid.nl is the website (not the Danish one)
—
}
li#menu-item-2 {
height: 15px;
background-image: url(https://www.off-thegrid.nl/wp-content/uploads/engels-vlaggetje_80px.png);
background-size: contain;
background-repeat: no-repeat;
background-position: 50% 50%;
}
li#menu-item-2 a {
opacity: 0;
}

Hi Rikard,
I want the image of the english flag to be seen next to the last menu item Contact. And when you click on the image, you must go to the english page:

I searched how to find out what my menu-itemnumber is. See the private content.
What am I doing wrong?

Hi Rikard,
Wauw, thanks a lot!
The only thing now, is that the image is twice so big as I want, is there a way to change it?
Or should I make a smaller image and then place that one in the code in the Quick CSS. What is the best solution?
Best regards, Jolanda

Hi Rikard,
I upload a 40 px. image and change the image url also in the CSS.
But the big image is still there. Can you please help me one more time? (I hope for the last time for this!)
Kind regards, Jolanda

Thanks Ismael for your answer
I add your code (with the right menu-item) to the quick CSS, but it didn’t make the flag smaller…
Can you please take a look, what am I doing wrong?
I send you the data in the private content.
Kind regards Jolanda

Rikard thank you so much for your help; this is exactly what I want :-)))!
What did I do wrong? I don’t understand it.
But you both helped me very gooed, thanks a lot!!!
Kind regards, Jolanda

Hi Rikard,
I still don’t understand it completely (unfortunatly I’m not a html-code-expert:-( ), but the most important thing is: IT WORKS PERFECT!
So yes, you can close the topic.
Again thanks a lot!