"Like but," is not an acceptable use of English except among teenage girls. It has no real meaning and doesn't make sense. If you were to use "but" in a proper sentence you would be using it part way through a sentence which expresses two opposing ideas separated but "but" and " , " is used before "but" not after. For example: "I'd like to go to the swimming pool, but I don't like to swim" "However" is a more complex word and can be used to replace "but" but can also mean "yet", "in spite of", or "whatever way". Examples: But and yet: "I'd like to go to the pool; however, I cannot swim." Notice the use of the semi-colon. This is the correct punctuation but is one that is in the process of change as it is rarely used with most replacing it with " , " In spite of: "She did, however, pass the test." This implies that there was an obstacle in her path that she managed to over come so she passed the test in spite of the obstacles. Whatever way: "I will help however I can"

Both could be a conjunction or an adverb (or other things). As it would be extremely time consuming to explain in details their functions in every situations, I will just answer your question. « But » has normally the comma BEFORE, and it is used as a coordinating conjunction. I like to cook, but I don't like to swim. « However » has normally the comma AFTER, and in this context, it is used as a coordinating conjunction, as well. I like to cook. However, I don’t like to swim. When « but » and « however » are used this way, they basically express a contrast; « however » expresses the contrast a little bit more, though. I hope that makes sense.