Even my Japanese co-workers struggle with words like 暖かくなかった, so you shouldn’t beat yourself up too much for that one.
I still struggle with nailing つ and づ.
I’m from sweden. I have trouble saying words with a a lot of S and Z sounds in them. For example
続く 「つづく」
涼しい「すずしい」
I can get them mostly right. But my japanese firends always tells me that I’m a little of on the second Z sound.
And sometimes I forget to not hold on the vowels so that for example 旅行 りょこう gets 良好 りょうこう
I find it hard to pronounce words that have ん followed by an r character (らりるれろ）
(My native language is English)
That one drove me crazy at first. I seem to have it down pretty good now. The new one I am struggling with it is 心理 (しんり) . It’s such a pain. Sometimes I seem to be able to hit it perfect, and then all the sudden sometimes I can’t do anything.
I’m a Dutch native speaker. For me, りょう is usually fine, but I’m currently struggling with んりょう, like in 完了（かんりょう）. The “r” almost disappears when I say it at normal speed, and when I slow down it plainly sounds weird.
Spanish native speaker here. I find that the sounds in Spanish and Japanese are very similar! The soft R, for instance, though its more rolled in Japanese, is quite similar to Spanish.
The greatest difference is the Z sounds. In certain parts of Latinamerica we’ve mostly lost the Spaniard Zed, and pronounce every Z as an S. so I just need to be mindful of actually pronouncing the Z (not that it’s a 100% identical).
My native language is Norwegian. I can’t distinguish between す and ず, and つ and づ very well in speaking or listening. Other than that Japanese is actually pretty easy for a Norwegian, pronunciation wise. We share many of the same sounds. The only real problem is the completely different pitch accent… I end up stressing the wrong part of words all the time.
Yup. This and long/short vowels do it for me.
This actually happened really early. Most Spanish colonists came from Andalucía, in the south of Spain, where this distinction had mostly disappeared in favour of one or the other. By the time their ships got to Canary Islands, most of the people on the boats had lost it (which makes Canary Spanish so hard to place!).
So the Spanish that got to the Americas was a completely new monster because it came from months of these people living in close quarters and changing each others way of speaking. That went to influence the way all of Latin American Spanish is spoken.
I often joke with my Spanish friends that their “official” variety is actually a minority language. 
My SO minored in Japanese, and she’s complained many a times how weird the ん to らりるれろ transitions are in the past. It’s only now, 3 years after, that I finally understand her woes.
And of course, she laughs at me every time I bring it up, the rapscallion.
りょ and りょう are the devil. I’m Dutch, for reference btw.