Afghan Peace talks have entered to their most crucial phase. The US and Taliban may agree on counter-terrorism assurances by the Taliban and troop withdrawal by the US.
Once everything is finalized on these two issues, then the Afghan government and politicians will start intra-Afghan negotiations with the Taliban on a political settlement and a comprehensive & permanent ceasefire. 
However, there are certain challenges and opportunities that require heed attention in order to reach a sustainable peace deal in the country. These include:
Challenges
The first challenge of the peace talks is the US withdrawal. The US invaded Afghanistan because Al-Qaeda had attacked the US and destroyed the twin towers and killed hundreds of the US citizens. After 18 years of war, the US not only has not eliminated Al-Qaeda, but currently ISIS and many other terrorist groups operate in Afghanistan. These terrorist groups are considered a major threat to the US, Russia, India and China. How the US will ensure when it signs an agreement with the Taliban, its interests will not be threatened by ISIS, Al-Qaead and the more conservative part of the Taliban?
The second challenge is the Taliban’s mindset. As the behavior of the Taliban show, they nearly hold the same perspective about the governance system in the country; they insist on the Emirate and deny the Republic. Many Afghans believe that Accepting the Emirate system, means returning back to the past and starting a new round of conflicts in the country. Further, under an Emirate system, we will lose all the achievements gained during the past 18 years.
The third challenge is the interference of the neighboring and regional countries. It is clear cut that different neighboring and regional countries have strategic interests in Afghanistan. These countries include Pakistan, India, Saudi Arabia, Iran, Russia, China and some south and Central Asian countries. It is not clear how the peace agreement will address the conflicting interests of these countries. 
Opportunities
Those Afghans, who believe in a democratic system, can form a united front to defend the democratic values and the current governance system against the Taliban. Some of these politicians are already part of the Afghan negotiating team. Thus, the Afghan government and Politicians negotiating team must be in close contact with different groups of the people during the Intra-Afghan talks in order to ensure that most of the concerns and modern values of the people are included in the peace agreement.
The second opportunity is the economic development in the country. Afghanistan has numerous mines and other natural resources that need investment. A peace deal will help Afghanistan to attract national and international investors to invest in different sectors in the country. Thus, Afghanistan may realize its vision as a country with strong economy, to become a regional economic hub and ensure the regional and international connectivity.
The third opportunity is the relative consensus of the international community and regional countries on the Afghan peace process. Currently countries including Pakistan, Iran, China, India, Russia, Central and South Asian countries and Arab countries have voiced their support of the Peace talks. The main question that remains unanswered here is that, Are these countries really interested in peace and instability in Afghanistan or they just look for an opportunity that the US leaves Afghanistan and then they start a new political game in the country?
The US and Taliban may soon reach to an agreement on the US troops withdrawal and giving a guarantee by the Taliban that  they will not let the terrorist groups to pose a threat to the US interests from Afghanistan . Then an Intra negotiations that lead to a political settlement and a comprehensive and permanent ceasefire in the country. As peace agreement is a compromise, it depends on the Afghan negotiating team how they can represent the Afghan nation to protect its 18 years achievements, democratic system and modern values.  It is clear cut that the US and international community support Afghans to preserve these achievements and universal values, but it is the Afghans who decide how to negotiate and preserve them.