Let’s add dialects to the mess:

While not written in “book” German*, colloquial German may feature des, dat, det or dit instead of das, shorten der to dr or elide parts (like the French l’, except it may be attached to the previous word): Das ist das Problem mit der deutschen Sprache -> Des isch’s Problem mit dr deutscha Sproach

(“That is the problem with the German language.” Bonus: notice how the demonstrative pronoun “that” is also
das? Just in case you were hoping it was restricted to “the”…)

* Hochdeutsch or Standarddeutsch (“High German” or “Standard German”), originally a written form slowly evolved over centuries to be most widely understood and has since been formalised. Informally, the term is also used for a spoken counterpart properly called Bühnendeutsch (“Stage German”), which isn’t always quite as “pure”, hence my distinction.

I bloody love my language.