A sentence I read on Wikipedia yesterday: "In contrast to speakers of Hindi and Urdu who claim they cannot understand each other even when they can, speakers of the varieties of Arabic will claim they can all understand each other even when they cannot." ;-)

This is assuming you learn Hindi to a good level beyond the Duolingo course (given it's very short). I cannot speak based on how much the Hindi course teaches, as I don't know that.

You will likely have minimal difficulty understanding colloquial Urdu, as some words are different in Urdu.

The formal language however is much different from Hindi.

The answer is Yes, you will be able to understand Urdu. I am a native Urdu speaker and i speak with my Hindi speaking friends without any problem. However, i learnt Devanagari script few years ago and now when i read Hindi fiction or newspapers, i can understand 70-80% of it as in written form there are a lot of Sanskrit words so sometimes it's very different than spoken Hindi.

In short, once you know Hindi, you will be able to communicate to anyone who speaks Urdu in colloquial settings.

The languages were considered identical a mere 70 years ago before they acquired religious dimensions. Even today, most linguists argue that Hindi and Urdu are registers of the same language---Hindustani. A speaker of Bazaar Hindi could easily understand (and speak) colloquial Urdu while she may not be able to so with some so-called "dialects" of Hindi including Bhojpuri and Haryanvi.

A lot of the basic vocabulary is the same. A couple hundred years ago, it was just one language called "Hindustani" written in different scripts. Recently, there have been more deliberate efforts to create distinctions but the core is the same. If you have a firm grasp on Hindi and another Arabic script based language, you should be able to pick up Urdu easily in my opinion. As far as the basics are concerned, its the same language written in different scripts but like OmegaGmaster pointed out, the formal vocabulary is very different and takes more skill to get right.

Man I have a friend his mother tongue is Urdu and mine is Hindi and we basically soeak the same thing with a few differences but we still can understand I tgink thats because we sprka informal and slang but formal urdu is different to formal Hindi somehow I can understand formal Urdu sometimes but some people can't.

You'll definitely be able to understand the gist of the conversation, there are very slight differences in the vocab and intonation but overall there are more similarities than there are differences when it comes to conversation

Depends on how good your Hindi is, but yes. Urdu is my mother tongue and I learnt the Hindi script in a few weeks and practiced like crazy, and now I can read and write quite well for almost 3 years now.

Yes, but many words are different. Apart from Urdu, you can also understand the Punjabi language which is also close to Hindi.

Yes you will be able to understand it but their alphabets are different.

If you're interested in contributing to adding Urdu to Duolingo - comment/vote on the following post! https://forum.duolingo.com/comment/8699437 also try to apply to becoming a contributor for "Urdu" for "English" Speakers! Here: https://incubator.duolingo.com/apply