I have been learning chinese for 10 months. 我学了10个月汉语了。✓ 我学汉语有10个月了。✓ 我学汉语学了10个月了。✓ 我学了10个月的汉语。乄 It implies that you learned Chinese for 10 month, and you're not learing currently.. 我学汉语学了10个月。乄 Same as above

answer: 我学了10个月汉语. which means I have been learning chinese for 10 months or I have been learning chinese since 10 months ago

The point of question is“How long” ，isn't “Are you studying now” ，so you don’t have to add “在” in the sentence。。But “我学汉语10个月了” is better than “我学了汉语10个月” in here

Question: 你学汉语多长时间了？ answer: 我学了10个月. The "了" in the question is just an ending character, it implies "have done already". 我学了10个月<- I have been learning for 10 months. 我已经学了10个月<- I have been learning for 10 months "already". "已经" put more emphasis on the time duration. Please note when we replying a question, we usually omit the object if it is already used in the question. The following are just fine but you can safely remove the words inside the () without effecting the meaning. 我学了10个月(的汉语) 。 我有 <-- it means you own something / had done 我有一只手表 （ I have a watch ） 我学过汉语 / 我有学过汉语 （ I had learned ....) It is difficult to translate "have been learning" to Chinese directly. 我在学了汉语10个月 <-- this is not natural If you want to use "在", the correct way is, 我在学汉语，10个月了。 Simply...我学了10个月 will be fine. It is a short form and very natural in conversation.

我已经学了10个月的汉语了 Or 我学汉语学了10个月