Wouldn't you liaise the words using hazat-wassl? I.e.: write أحب ٱلصيف
Yes, you should. I don't get how duolingo "vocalized" the texts, it feels wrong sometimes.
Why is اَلْصَّيْف written with the sukun on the لْ? Isn't it silent and therefore not vocalized in this situation?
Yes, you're right.
لا أحبُّ الصَّيفَ الباردَ.
"laa 2uHibbu aS-Saifa al-baarida" / "laa 2uHibbuS Saifal baarida"