Can we use however and although in one and the same sentence?
However, although there is small room for improvement.
Although he's small, my parrot's very strong.
My parrot's very strong, although he's small.
Although takes a finite clause, a mini-sentence, as a complement. Together, they form one phrase. In the examples above, we can see that this phrase can come before or after the main part of the sentence. This phrase contains extra information relating to the main clause. Notice that the word although has to be at the front the subordinate clause because it's part of the same phrase.
However on the other hand is an adverb. It isn't grammatically part of any other phrase in the sentence. Usually it contrasts the sentence it appears in with the previous one. It can appear in different places in the sentence, at the beginning, in the middle or at the end.
She's not very big. However, she can jump very far indeed.
She's not very big. She can jump very far indeed, however.
She's not very big. She can, however, jump very far indeed.
If we want to contrast a sentence using although with the sentence before it, we can do this using however.
The people in reception were always efficient and willing to take extra time to help us. However, although the rooms are large and modern, there were still all kinds of problems.
Here, however is contrasting the the problems with the nice reception staff. Although is contrasting the problems with the nice rooms.
The Original Example
There is a small problem with the Original Poster's example, which is that we have an although phrase, but no main clause! We could add another clause on to make it grammatical:
Hope this helps!
It is certainly possible to use almost any two words in one and the same sentence (although some people would argue that's impossible if the words are honest and politician), however, the sentence could become quite long.
See what I did there?
Yes you can use them in one sentence. But you can not use them "together", they have to have a separate function in the sentence:
Finding money is usually difficult. In this case, however, although the costs are high, the management has promised to pay the bill.
Here, the clause with although can be left out without changing the main meaning of the sentence.
Your example sentence is not correct as a sentence. It could be the beginning of a correct sentence, but just like this, however is feeling a bit lonely :)
You can always try to fix all the last little details. However, although there (still) is small room for improvement, we will consider project finished.