Note that in Icelandic there are also the palatal cononants, shown above in GREEN.
Compare this figure with the figures showing articulations on p.33, in Roach, figs. 11 12 and 13.
So English has three, Icelandic four, articulatory positions for the plosives.
You should try to hear the difference between English 'came' and Icelandic 'keim', and between English 'game' and Icelandic 'geim': say these words aloud to yourself.
|came - keim|
|game - geim|
Practice your own pronunciations of 'coat, kite, Kate', using both English and Icelandic accents. And try saying 'ágæt kænska' as an English speaker would, using the k and g as in 'kite' and 'guy'.
If you have any questions mail me at firstname.lastname@example.org.