However,(যাইহোক) is a (Adversative conjunction)

1. Used when you are saying something that seems surprising after your previous statement, or that makes your previous statement seem less true
   Diamond mining is a highly profitable industry. There are, however, certain risks involved.(হীরা খনি একটি অত্যন্ত লাভজনক শিল্প। যাইহোক, কিছু ঝুঁকি জড়িত আছে.)
2. Used when you are changing the subject
   I’m delighted I could be here today. However, I didn’t come here to talk about myself.(আমি আজ এখানে থাকতে পেরে আনন্দিত। যাইহোক, আমি এখানে নিজের সম্পর্কে কথা বলতে আসিনি।)
3. Used for saying that it makes no difference how good, bad, difficult etc. 

• However, good/well/bad/badly/hard etc.: She would still love him however badly he behaved.
• However, much/many: We’re determined to have a wonderful holiday, however much it costs.
• However, long something takes: We are determined to solve this problem, however long it takes.